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Cyanobacteria (Blue-green Algae)


  1. (Summary) Erythromycin vs Blue-Green Algae - a short article
    by (Richard Clark) (Tue, 17 Nov 1992)
  2. Cyanophyta (was Chloramine==Ammonia??)
    by (Michael Riehle) (Sun, 21 Aug 1994)
  3. Cyanophyta (was Chloramine==Ammonia??)
    by ac554-at-FreeNet.Carleton.CA (David Whittaker) (Sun, 21 Aug 1994)
  4. Cyanophyta (was Chloramine==Ammonia??)
    by ac554-at-FreeNet.Carleton.CA (David Whittaker) (Sun, 21 Aug 1994)
  5. blue-green algae & erythromycin
    by (Shaji Bhaskar) (14 Mar 1995)
  6. [F/M]Blue-green algae and erythromycin, a summary. (long 8k)
    by (Tony Clementz) (7 Feb 92)
  7. Blue-green algaeĆ¢acteria correlation
    by (David R Friga) (Sun, 5 Jul 1992)
  8. Blue-greens
    by Erik Olson <(e-mail)> (Thu, 13 Jul 1995/1996)
  9. Bluegreen algae and the Grool
    by krombhol-at-felix.TECLink.Net (Paul Krombholz) ()
  10. Antibiotics for cyanobacteria
    by (Neil Frank) (Fri, 14 Jun 1996)
  11. Algae-fighting plants
    by (Paul Krombholz) (Thu, 7 Nov 1996)
  12. blue-green algaes & NO3 low ?
    by "James Francis Redfern" <> (13 Nov 1996)
  13. Re:cyanobacteria
    by (Paul Krombholz) (Sat, 18 Jan 1997)
  14. Nutrient limitation
    by "David W. Webb" <dwebb/> (Wed, 10 Dec 1997)
  15. To get rid of blue green algae
    by Shawn Young <srly.dont_want_no_spam/> (Thu, 22 Jan 1998)
  16. BGA Anecdote
    by George Booth <booth/> (Wed, 21 Jan 1998)
  17. Seachem Flourish Question
    by Mark Fisher <Mark.Fisher/> (Wed, 23 Dec 1998)
  18. Seachem Flourish Question
    by "Roger S. Miller" <rgrmill/> (Wed, 23 Dec 1998)
  19. Cyano Preliminary Results
    by Mark Fisher <Mark.Fisher/> (Tue, 5 Jan 1999)
  20. Black BGA in plantless tank
    by krandall/ (Tue, 12 Jan 1999)
  21. Cyano Preliminary Results
    by Neil Frank <nfrank/> (Sat, 02 Jan 1999)
  22. Antibiotic Treatment of Cyanobacteria
    by "Roger S. Miller" <rgrmill/> (Sun, 17 Jan 1999)
  23. (No Title)
    by ()
  24. Maracyn
    by "Chuck Lawson" <lawson/> (Sun, 17 Jan 1999)
  25. Erythromycin and breeding pairs?
    by "Maladorno, Dionigi {DRUG~Nutley}" <DIONIGI.MALADORNO/ROCHE.COM> (Fri, 16 Apr 1999)
  26. Beating back bluegreen algae
    by "Roger S. Miller" <rgrmill/> (Wed, 25 Aug 1999)
  27. Battling BGA
    by George Booth <booth/> (Wed, 2 Aug 2000)

(Summary) Erythromycin vs Blue-Green Algae - a short article

by (Richard Clark)
Date: Tue, 17 Nov 1992

This may be asking a lot, but in the brief article I wrote below I
tried to summarize some of the information I have read on the net
concerning blue-green algae.  In a couple of places I refer to
``someone'' saying something on the net, if you know who said it I'll
be glad to credit the person in the text.  I wanted to reference
George and Karla Booth's recent series in AFM as a good place to get
information, but I don't know what months it ran (or is still
running).   Could someone tell me?

I will submit the article to a local aquarium club bulletin (only
non-profit places), not to any fishy mags - as if they'd accept it.
If someone wants to use it I don't mind as long as I'm informed.
Since the material is largely summarized from the net, I was hoping
someone would take the time to read it, and point out any inaccuracies
that may be present.  It is approx 140 lines of text in LaTeX, but
readable by non-LaTeXperts.  LaTeXed, it is slighly less than 2 pages.

Thank you

rick clark


\title{Battling with Blue-Green Algae} 
\author{\copyright Richard Clark, Montreal Aquarium Society
\thanks{May be freely distributed or reproduced only for
non-profit use, as long as no modification is made to the text, title,
or this notice.  Montreal Aquarium Society, P.O. Box 653, Station B,
Montreal, Que. CANADA, H3B 3K3}}

\date {November 8, 1992}


If you have a heavily-planted fish tank, you know that your worst enemy
isn't ich or fungus - it's algae.  Typically, the fish in the tank
cost far less than the plants.  It's a crime what a little neglect
can do to a well-planted tank.  Miss a few water changes, add a
little pH buffering solution to your water, have strong light, use
some plant fertilizer, and chances are you'll be looking at algae that
will cost you plenty of green stuff.

It has happened to me. I used fertilizers as recommended on the
packages, added Wimex iron supplement, had 2 20 W fluorescent tubes on
top of the 75 $\ell$ tank, and had pretty good plant growth.  My
Apongeton crispus were flowering, my Echinodorus bleheri were
flowering -- I was on top of the world.  Then it happened.  A dark green algae
started to cover some of the plants.  I thought - ``no sweat'', I bought
the algecide from Aquarium Pharmaceuticals, placed the recommended
amount into the tank, and watched my fish (mostly tetras, but also a
plecostamus) go crazy trying to jump out of the tank.  I rapidly did a
50\% water change which seemed to calm the fish down, and did another
50\% water change the next day.  I noticed that the nice green algae
was dead, but the ugly stringy stuff and the dark green slimy stuff
was doing great. Algecide was definitely not the right treatment.

I tried the ``old-fashioned'' approach to reducing the algae - I shut
off the lights for a few days. The Hygrophila polysperma, already
weakened by the algae, all but died and I had to pull it out of the
tank.  The A. crispus died back, and I had to pull off numerous leaves
from the E. bleheri.  I now only had about 1/3 of the plants I
originally had, but I was reasonably algae-free because I had thrown
out everything with algae on it.

Over the next few months I purchased a few more plants, including some
from the club auction, but unknown to me, those had algae on them.
Guess what?  I was in trouble again.  I didn't notice it at first
because the algae was close to the stem on my cabomba and not on the
leaves where it would be easily visible.  This time I tried a more
systematic approach, I used my computer to find help.  I have access
to a world-wide network of computers (Internet), and read
``newsgroups'' about tropical fish. One guy reported that the dark
green ``algae'' one sees in tropical fish tanks is not really an
algae, but a bacteria. He reported great success in using the
anti-bacterial drug erythromycin (available at pet shops, trade name
for it is Maracyn - not Maracyn II).  In fact, blue-green algae are
not bacteria, but share many of their characteristics \cite{Bake77}.
Erythromycin works by attacking the cell wall of the bacteria
\cite{Dixo92}.  I figured I didn't have much to lose, so I bought
some, removed the carbon from my filter, used the recommended dosage,
and miracle of miracles, the ``algae'' died off without affecting the
other plants or fish.

The miracle cure wasn't without drawbacks though.  Although the
instructions on the package specifically state that Maracyn does not
affect Nitrosomonas and Nitrobacter bacteria (those responsible for
the nitrogen cycle in the tank), I immediately noticed a rise in
ammonia levels.  The depletion of nitrifying bacteria by erythromycin
is also reported in \cite{Dixo92}.  I used Amquel to remove the
ammonia, and continued to use it until water changes reduced the
amount of erythromycin in the tank, and the filter was again working
properly (about 2 weeks). Through interactions with other people on
the internet, it appears that freshwater nitrifying bacteria suffer
more than saltwater ones from this treatment, but this is only a
casual observation and I'm not ready to commit to that statement yet.
I'd be happy to hear about your experiences to see if this theory is

Over 100 varieties of blue green algae are found all over the
world\cite{Bake77}.  It's hard to avoid getting any in your tank
because the spores are in the atmosphere, and  plants you put in the
tank are likely to contain some.  Although high nitrates are usually
suspect when blue-green algae begins to grow, Vinny Kutty reports
\cite{Kutt92} that it can grow even in water that is almost absent of
nitrates (because it can fix atmospheric nitrogen) -- provided there
are phosphates in the water. Kutty reports that a level of 0.5ppm of
phosphates in a river is considered ``polluted'', but that phosphate
levels below 0.5 ppm may retard plant growth.  My guess is that a
level somewhat below 0.5 ppm would be a good target for phosphates, and
about 10 ppm or below for nitrates (freshwater). 

There are a couple of ways to keep nitrates and phosphates at low
levels.  You can either try to keep their introduction to the tank
low, or you can get them out of your tank once they are there.  In the
latter category, there are of resins that can be used and the old
standby -- water changes.  To make sure the phosphates and nitrates
don't get in your tank, note that many plant fertilizers contain these
components, so use them sparingly (see below).  If you use a product
that buffers the pH of your water, it likely contains phosphates.
Novaqua, a common water additive, will result in 5 ppm phosphates if
used as directed.  Overcrowded tanks are a cause of phosphates from
fish waste \cite{Kutt92}, and of course, with a working biological filter,
ammonia is eventually converted to nitrates.  PH Down, a product which
lowers the pH level of aquarium water uses phosphoric acid, so that
might not be a great idea either. Finally, check your water supply, it
may be the source.

I don't want this article to be a complete downer regarding keeping
plants, so I'll just summarize quickly some of the points I have
gathered from my internet reading.  Fertilizers are not generally
recommended in planted tanks because of the potential algae problems.
Trace elements and iron are all that should be used, fish provide the
rest of the fertilizer.  You must provide sufficient light for the
plants to grow, this is the most common problem people have with
plants. About 40 W of fluorescent light on a 75 $\ell$ tank is about
right \cite{Jame88}.  I use one full-spectrum bulb and one
``plant-bulb'' on my tank.  You have to provide sufficient gravel for
the plants to grow, about 8-10 cm of 1 or 2mm gravel is okay.  Water
changes are important, they help to reduce any pollution that may be
present in your tank.

I wish you luck in keeping your plants healthy, use the guidelines
I collected above to try to reduce the chance of algae infestation in
your tank.  If the choice is between losing your plants or using
Maracyn, use it, but keep a close eye on the ammonia level.  Don't
depend on using this drug to combat all algae, just blue-green algae.
Remember that using anti-biotics on a casual basis can result in
strains of bacteria that are resistent to the anti-biotic - so be
careful.  A few good references on keeping plants in an aquarium are



-at-book {Baen91,
 author   = "Dr. {R\"{u}diger} Riehl and Hans A. Baensch",
 title    = "Aquarium Atlas",
 edition  = "3rd",
 publisher= "Tetra Press/Baensch",
 address  = "201 Tabor Road, White Plains NJ.",
 note     = "ISBN 3-88244-050-3",
 year     = 1991

-at-book {Bake77,
 author = "Jeffrey J.W. Baker and Garland E. Allen",
 title  = "The Study of Biology",
 edition = "3rd",
 publisher = "Addison-Wesley",
 year = 1977,
 note = "ISBN 0-201-00349-X"

-at-article {Dixo92,
    author = "Dr. Beverly A. Dixon",
    title = "Antibiotics -- How do they work?",
    journal = "Aquarium Fish Magazine",
    month = feb,
    year = 1992,
    pages = "54-59"

-at-book {Jame88,
 author   = "Barry James",
 title    = "A fishkeeper's guide to aquarium plants",
 publisher= "Tetra Press/Salamander Books",
 address  = "201 Tabor Road, White Plains NJ.",
 note = "ISBN 3-923880-57-X",
 year = 1988

-at-article {Kutt92,
    author = "Vinny Kutty",
    title = "It's about Algae",
    journal = "Aquarium Fish Magazine",
    month = may,
    year = 1992,
    pages = "40-48"

rick clark ( | Ban Handguns.
           (CIS 70272,3270)            |

Cyanophyta (was Chloramine==Ammonia??)

by (Michael Riehle)
Date: Sun, 21 Aug 1994
Newsgroup: rec.aquaria

Erik Olson ((e-mail)) wrote:

: I'm real curious about this.  I have NEVER been able to get blue-greens
: to go away with water changes, and I've tried the whole spectrum of them.
: What usually happens is the carpet I pull out grows back even quicker from
: the bits remaining.  I'm guessing this is becuase it's just outcompeting the
: plants for any available nutrients.  I would like to hear of people's
: experiences in treating cyanophyta WITHOUT erithromycn.  How did it go
: away?  gradually?  Did you vaccuum up large carpets or leave them
: there?

I'm not sure I can say much except that I just did massive (80%+) water
changes every two weeks and cleaned up the "carpets" of cyanbacteria
with my gravel vac at the same time.  If I do this faithfully, the
problem is gone in two or three water changes.  In general, the only
time I've had a problem with the stuff is when I've failed to do
my water changes every two weeks and it's been introduced somehow.

But it occurs to me that most of my cichlids dig pretty industrially
and keep the gravel stirred.  This may also be a factor.

Michael Riehle     
CIS: 76450,26          
               #include <std.disclaimer>

Cyanophyta (was Chloramine==Ammonia??)

by ac554-at-FreeNet.Carleton.CA (David Whittaker)
Date: Sun, 21 Aug 1994
Newsgroup: rec.aquaria

>>: Maracyn is the only "medication" I've ever bought in the last few years,
>>: aside from Ich treatment.  It does an amazing job at nuking blue-green
>>: algae (once you have found and eliminated its source of nutrition, of course,
>>: so it doesn't come back later!).  Generic Erithromycin should work just
>>: as well.

>I'm real curious about this.  I have NEVER been able to get blue-greens
>to go away with water changes, and I've tried the whole spectrum of them.
>What usually happens is the carpet I pull out grows back even quicker from
>the bits remaining.  I'm guessing this is becuase it's just outcompeting the
>plants for any available nutrients.  I would like to hear of people's
>experiences in treating cyanophyta WITHOUT erithromycn.  How did it go
>away?  gradually?  Did you vaccuum up large carpets or leave them

Floating plants and perseverance sometimes work for us. There seems to be a
seasonal aspect to the growth of blue-green algae. Others swear by anti-

Cyanophyta (was Chloramine==Ammonia??)

by ac554-at-FreeNet.Carleton.CA (David Whittaker)
Date: Sun, 21 Aug 1994
Newsgroup: rec.aquaria

In a previous article, (Michael Riehle) says:

>Erik Olson ((e-mail)) wrote:
>: I'm real curious about this.  I have NEVER been able to get blue-greens
>: to go away with water changes, and I've tried the whole spectrum of them.
>: What usually happens is the carpet I pull out grows back even quicker from
>: the bits remaining.  I'm guessing this is becuase it's just outcompeting the
>: plants for any available nutrients.  I would like to hear of people's
>: experiences in treating cyanophyta WITHOUT erithromycn.  How did it go
>: away?  gradually?  Did you vaccuum up large carpets or leave them
>: there?
>I'm not sure I can say much except that I just did massive (80%+) water
>changes every two weeks and cleaned up the "carpets" of cyanbacteria
>with my gravel vac at the same time.  If I do this faithfully, the
>problem is gone in two or three water changes.  In general, the only
>time I've had a problem with the stuff is when I've failed to do
>my water changes every two weeks and it's been introduced somehow.
>But it occurs to me that most of my cichlids dig pretty industrially
>and keep the gravel stirred.  This may also be a factor.
Cyanophyta are able to fixate free nitrogen gas, an advantage they have
over plants. This may explain their ability to bounce back after a
water change.

blue-green algae & erythromycin

by (Shaji Bhaskar)
Date: 14 Mar 1995
Newsgroup: sci.aquaria

In article <>,
David Whittaker <ac554-at-FreeNet.Carleton.CA> wrote:
>In a previous posting, chris t durkin ( writes:
>>      Ethromycin is an antibiotic, and is should be used ONLY to treat
>>  disease, not to eliminate cyanobacteria.

>A one time dose of 1/2 the recommended dosage will eradicate blue-
>green algae indefinitely. At a maximum that is 1/10 the amount
>required in the treatment of those diseases for which EM is most
>commonly employed. Of course after one has done this one must
>ensure that the conditions exist for the plants to grow and thus
>prevent the algae from regaining a foothold. In other words, it
>should be a one-time affair.
>Much more damage is done by the sometimes indiscriminate use of
>various medications with the consequences that you have highlighted.
>At the low dosage effective against the algae, I am not at all
>sure that the nitrosomas and nitrobacter are profoundly affected.
>It seems to me that there was some previous discussion and doubts
>raised about this. Do you know any different?

Lowered doses, and shortened dosing periods, significantly raise the
chances of producing resistant strains.  If you use the medicine at 
recommended strength for the entire recommended duration, you are 
less likely to build resistance.

About nitrifying bacteria being affected: Erythromycin is primarily
effective against gram positive bacteria, and I belive most nitrifying
bacteria are gram negative.  That being said, I have had instances
where the tank had to re-cycle after it was treated with Erythromycin.
Go figure.

Shaji Bhaskar                                    
BNR, 35 Davis Dr, RTP, NC 27709                            (919) 991 7125

[F/M]Blue-green algae and erythromycin, a summary. (long 8k)

by (Tony Clementz)
Date: 7 Feb 92
Newsgroup: rec.aquaria

       I've followed the postings about blue-green "algae"
and Maracyn (erythromycin) the last few weeks and the
following is an attempt to review some facts about
erythromycin (the active ingredient in Maracyn) and blue-green
algae, with special emphasise on the use of erythromycin for
treating blue-green "algae" infections.


       Thats right. The correct name is blue-green bacteria
(or cyanobacteria for those latin freaks out there). So
without going into a lot of details, blue-green algae is a
bacteria so an outbreak of the stuff in your tank is actually
an infection.
       It is important to know that blue-green bacteria
comprise a large and heterogeneus group of organisms. Not even
the color is the same. Some are green, some blue-green, and
some are red. They can be found almost everywhere in nature.
They are usually more tolerant to extreme environments than
"normal" algae and can be found in hot springs as well as
saline lakes. Drying your gravel and tank is subsequently not
an efficient way to get rid of them. Some species can even be
found in the middle of the dessert. Blue-green bacteria
efficiently absorbes light between 550-700 nm, which is
roughly the same as for plants and green algae.
       As we all know, they thrive in warm water, rich in
nutrients. However, many blue-green bacteria is not dependent
on nitrite, nitrate, or ammonia, since they can use molecular
nitrogen (nitrogen fixation). This all leads to the well known
conclusion - once established in the tank, they are a pain in
%&#-%&. I wonder how many potential aquarium hobbyist has been
lost because their first tank became covered in green slime
within six month.


       Bacteria can be divided into two groups, either Gram-
negative (G-) or Gram-positive (G+). This classification is
based on if the bacteria stains (+) or not (-) in a special
staining technique - the Gram staining (invented by Christian
Gram). Positive or negative staining reaction reflects a
fundamental difference in the structure of the cell wall of
the bacteria.
       Erythromycin is more efficient towards G(+) bacteria
than G(-). It is one of the safest antibiotics, meaning that
it does not affect plants, fish or animals. Blue-green
bacteria belongs to the G(-) bacteria but it is a special case
with respect to sensitivity to antibiotics (i'm on thin ice
here, but I think I am correct). They are more sensitive to
erythromycin than other G(-) bacteria. Fortunately, the
bacteria important for the nitrogen cycle (your biofilter) are
of the G(-) type and are much less sensitive to erythromycin
than the blue-green bacteria. So your biological filter is
"fairly" safe.
       The reason that some tanks experience an ammonia peak
after treatment with erythromycin is (probably) not because
the biological filter is non-functional. It is more likely
that it is because of the high content of protein released
from the dead blue-green bacteria which is broken down to
ammonia and/or nitrite by the "good" nitrifying bacteria in
your biofilter. This boost of protein to be broken down upsets
the finely tuned balance of different bacteria in your filter.
(Actually, if you killed of all bacteria in your tank and
filter, you would never get ammonia).
       In many countries in Europe there are restrictions on
buying antibiotics. You usually need a prescription. I suggest
contacting a vet. If he can prescribe antibiotics for a mouse
I'm sure he can do the same for your tank. Remember, your tank
is infected.


       First a few things NOT to do (my own, very personal,

       If you have an established infection, do not try to
get rid of it by turning the lights of. Most likely this will
get you into more trouble. Your going to kill of the "good"
algae and the plants, but the blue-green bacteria is going to
return when you turn the lights back on (usually more fiercly
than before).

       Personally I don't like copper. Copper is poisonous to
everything - plants, fish, and bacteria. At least in Europe,
most "miracle" treatments you buy contains copper.

       You could try manually removing the blue-green algae,
combined with extensive water changes. But in my experience
it's fruitless, unless you spend all your free time with your
fingers in the green slime. Ever tried to clean the stuff away
from Cabomba or Java fern? Then you know what I mean.


       Of course, tank hygien is important. Regular water
changes and all that. But for those who has been doing it all
according to the textbook and still wondering if your doing
something wrong, don't despair, you have'nt been hit by a
blue-green curse.
       Me myself, I get an infestation in about every second
tank (freshwater) I set up. These does not correlate to any
increase in ammonia, nitrite, or nitrate (I do not keep check
on phosphate, but I plan to). One exception is tanks with soft
and acid water. You rarely find blue-green bacteria in these
tanks since most bacteria, including blue-green, do not like
acid conditions.
       The followin is my suggestion for battleing blue-green

       First make sure that it is blue-green bacteria and not
the "normal" algae. Remember that erythromycin is ineffective
on anything but bacteria.

Day 1.
       Add 2.5 mg/L erythromycin. If you have a protein
skimmer, turn it off. I believe it will inactive a lot of the
antibiotic through coprecipitation with protein. It will,
however, be very usefull later.

Day 2.
       Add 2.5 mg/L erythromycin.

Day 3.
       Now you should see a lot of dead blue-green bacteria
floating around in the tank. Increase filtration (a second
mechanical filter if possible) to get rid of it. If you have a
protein skimmer, turn it on. The critical thing now is to get
rid of as much protein (dead bacteria) as possible to avoid a
peak of ammonia.

Day 4.
       Most blue-green bacteria should be dead by now. Try to
clean out as much as possible of the dead stuff. I use a jet
stream of water from the outlet of a canister filter to remove
it from plants and decorations. Combined with the second
mechanical filter, this works fine for me. Let the filter work
for a couple of hours then make a 50% water change. Add 2.5
mg/L erythromycin.

Day 5-7.
       Wash the mechanical filter at least once a day. Keep
check on ammonia and nitrite but do not change any water
unless absolutely necessary. The extra filter can be removed
as soon as the water clears up.

Day 8.
       Make a 30% water change. Add 1 mg/L erythromycin.

From now on, resume your normal maintenance.

       The concentration I use is in theory a bit high and
getting up where it should starts having an effect also on G(-
) bacteria. When I started using erythromycin I had problems
using lower concentrations in the tank. It was not very
effective. It might be time to check it again.

       One word of caution. Only use erythromycin when you
really need it or you might end up with blue-green bacteria
resistent to the antibiotic.

       My practical experience of using erythromycin to
battle blue-green bacteria is limited to my own few tank (and
some friends). It would be interesting to get some feedback
from people with experience (good or bad) of battling blue-
green bacteria (with or whithout erythromycin). I would of
course post a summary of the response.
Tony Clementz		|	Email:
Dept. of Microbiology	|		  or
University of Lund	|	Internet:
Solvegatan 21		|	BITNET:	  BIOGEN6-at-SELDC52
S-223 62 Lund		|	Phone:	  +46 46 104451
SWEDEN			|	Fax:	  +46 46 157839

Blue-green algaeĆ¢acteria correlation

by (David R Friga)
Date: Sun, 5 Jul 1992
Newsgroup: rec.aquaria

I hope this doesn't come too late.  I work at a place where
a lot of microbiology takes place and so dug up this piece of
information on blue-green algae.  This information is from the
"C.R.C. Handbook, Practical Handbook of Microbiology".
It reads as follows:

Blue-green Algae (Cyanobacteria)
        ...As Stanier et al. originally pointed out, although they
(cyanobacteria) have cell walls similar to those of Gram-negative
bacteria, there are fundamental differences between the pigments
and overall photosynthetic processes of blue-greens and those of
phototrophic bacteria.  ...Thus, it appears that the cyanobacteria
are truly an intermediate group between the higher algae and plants
and the bacteria.  Since classifications in taxonomy should be as 
rational and useful as possible, it would seem reasonable to place
these organisms in a kingdom of their own, distinct from either the
bacteria or the higher algae."

       I also tried to dig up info on nitrosomous (sp.) bacteria.
As I am not sure of the specific species involved in cycle itself,
and there are several, I could not get any pertanent info., other
than one resounding fact.  They all appear to be listed as
Gram-negative bacteria.

	I will leave it up to you to draw your own conclusions
concerning the correlation between these two facts, because I am
basicly a lazy person who dislikes real lengthy posts.
	Thankyou for taking the time to read this and if there
are any queries or comments, please e-mail.
		Dave  (dfriga-at-magnus)


by Erik Olson <(e-mail)>
Date: Thu, 13 Jul 1995

Don't have the bandwidth to fish through the digest for the article, but
someone posted Blue-Green algae is an indicator of low light.  As George 
noted, this is very untrue.  I mentioned in the last week that I am 
experiencing a small b/g outbreak, but only in two places: the area of 
the tank getting direct sun all day & not subject to the "Behle/Dennerle" 
tricky midday storm dark period, and in the inside of my overflow siphon 
which is right next to the light.

Now, one thing I have noticed is that blue-greens appear different under 
different light conditions.  In very low light, they take on a dark, very 
bluish hue, while in the high-light tank they have an almost kelly-green 

  - Erik

- ---
Erik D. Olson                                   (e-mail)
Not at home, probably at work (Wo-hoo!)

Bluegreen algae and the Grool

by krombhol-at-felix.TECLink.Net (Paul Krombholz)

My five-year old daughter has discovered Goosebumps books, written by R.I.
Stine, who is currently monopolizing the kiddie horror book market.  I have
read four Goosebumps books to her, and one of them had a monster in it that
reminds me of bluegreen algae (Cyanobacteria).  The monster was called the
Grool, and it was sort of like a sponge, but when somebody found it, it
started bringing that person bad luck.  That unfortunate person was then
forced to keep it, because, if it were given away, its former owner would
die in one day, Now, I am not saying that bluegreen algae is like that, but
it does have some properties in common with the Grool.  The Grool could not
be destroyed by physical means.  It always reconstituted itself.
Furthermore, it thrived on the misfortune and hatred of its owner and any
others who were nearby, who also had bad luck.  The more strenuous the
efforts to get rid of it, the happier it was.  Are you starting to see some
similarities with bluegreen algae?

Our heroine tried various ways to destroy the Grool, none successful.
She even tried putting it through the garbage disposal grinder, but it
popped back, cackling with glee. When all seemd to be lost, she came up
with the idea of  witholding the hate and dislike that it thrived on.  She
held it, sang little love songs to it, and kissed it.  It soon stopped
breathing and withered away to some brownish fluff that blew away.

I have a fifteen gallon tank that recently had a bad bluegreen algae growth
covering a lot of my plants. There are no fish in the tank, only Daphnia
and some snails.  The ramshorn snails didn't want to eat the bluegreen
algae and were dying out.  Pond snails didn't like it either.  I had not
given the tank any nutrients for a long time, except some potassium.  The
plants or portions of them that were not covered with the bluegreen algae
looked yellow-green and nitrogen deficient.  So, like our heroine, I
started loving the algae.  I gave it more nutrients by adding some small
dried liver pieces.  As the liver pieces decayed, the snails started to
perk up and move around some more.  I took a half-teaspoon full of dried
liver, scattered it on some damp sand in a shoe box and let it get moldy
for about five days.  Then I rinsed the whole mess into the tank with
water.  The snails definitely were starting to grow.  The bluegreen algae
began to turn a dull brown and break up into clumps.  I added another bunch
of dried liver pieces composted on sand for a week.  Along with this, I
added iron DTPA, 0.5 mg Fe per liter.  Now the algae really looks sick and
there is less of it each day.  The snails are laying eggs and there are a
bunch of baby ramshorns cleaning off the glass.  The plants have turned a
nice green, and nearly all the algae has fallen off them.

The message is clear:  Don't try to get rid of bluegreen algae by starving
it.  Instead, pamper it to death.

Paul Krombholz                  Tougaloo College, Tougaloo, MS  39174
In cool, pleasant, Mississippi where it is cool if the high temp is below
90 and pleasant if the dew point is below 70.

Antibiotics for cyanobacteria

by (Neil Frank)
Date: Fri, 14 Jun 1996

>From: "Olive K. Charlsey" <>
>Date: Thu, 13 Jun 1996 16:33:53 -0400 (EDT)
>Subject: Antibiotics for cyanobacteria
>       I recently treated my tank with 2.5mg/l of erythromycin to get 
>rid of some cyanobacteria that were beginning to grow over my lileopsis. 
>The treatment worked for a majority of the bacteria, but there are still 
>a couple of small patches left after 4 days. Are there any other 
>antibiotics that can be used against Gram negative bacteria that 
>will not damage the plants or cause any other excessive harm? 

I once used Kanamycin when I could't find erythromycin. This is another
'mycin' sold in aquarium shops. It worked fine. I think others have also
used it on 'resistant strains of blue green algae (another name for
cynaobacteria). Regarding your use of erythromycin, you might want to wait a
few more days before you give up on its effectiveness. I have found that its
and other algicide's effects are not noticed immediately. You did not say
how many daily treatments of erythromycin you used.  The label for fish
disease recommends 1 200mg capsule per 10 gallon(40 liters), for several
days. This corresponds to 5.0 mg/l per day. As you also did, I usually try
1/2 dose or 2.5 mg/l. I have found this to be effective and notice that the
BG starts to decline within a week. After I gather up the blob of dead algae
together with other bottom debris and a little syphoning, it is (atleast
temporarily) gone! <g>  Yes folks, I TOO get BG algae. And it may
periodically come back. And my fish occasionally get ich (when I forget to
crank up the heaters in the late fall). These events seem to be the normal
course of nature. :-)

You might want to stay with the erythromycin before you go to another
antibiotic. We do not want you to be developing any super resistant strains
of BG bacteria.<RBG> You have several degrees of freedom left with the
erythromycin; if you haven't already done this.... you could double the
daily dose and/or increase the duration of treatment (up to label
recommendations). THis will give the erythro more capability to fully zap
any resistant cells. That's why the MD's tell their patients to treat an
infection for days (weeks) longer than the symptoms are present. 
If it were me, I would leave the filter going to kill the BG which may be in
the filter, but be prepared for a big die off of your nitrobacteria (both in
the filter and elsewhere). To be conservative, feed sparingly or nothing
during the treatment to reduce the chance of an ammonia/nitrite peak.
However, if you have lots of plants, you might not measure any ammonia in
either case. I have always found the plants to perk up after the antibiotic
treatments, either due the increase in light (once the bg is removed from
their leaves) or from the ammonia snack! I WOULD LOVE FOR SOMEONE WITH AN

N. Frank

Neil Frank, TAG editor    Aquatic Gardeners Association    Raleigh, NC USA

Algae-fighting plants

by (Paul Krombholz)
Date: Thu, 7 Nov 1996

>Subject: Algae-fighting plants
>According to Tropica Plants, Ceratophyllum Demersum exhibits
>"alleopathic behaviour". That is, it excretes substances that inhibit
>algae growth. Does anyone know if other plants do this? Do these
>substances also inhibit general plant growth or is the effect limited
>to algae?
>It seems that if this is true, then algae control could at least be
>given a boost by using bunches of plants that exhibit alleopathic
>Any thoughts?
>Kind Regards,

Ceratophyllum does seem to make bluegreen algae (cyanobacteria) go away,
and, in my experience, so does Hydrilla. The cyanobacteria doesn't seem to
be killed, rather, it seems to stop growing and slowly diminish to nothing
over a month or two.   Unfortunately, neither Ceratophyllum nor Hydrilla
has any effect on green water algae.

Diana Walstad has a good literature review of allopathy in aquatic plants
and algae, starting in Vol. 8, number 4 of The Aquatic Gardener.

Paul Krombholz                  Tougaloo College, Tougaloo, MS  39174
In chilly Mississippi, where I am hoping they can get the heat working in
the science building before the next cold front comes.  

blue-green algaes & NO3 low ?

by "James Francis Redfern" <>
Date: 13 Nov 1996
Newsgroup: rec.aquaria.freshwater.plants

Cyano-bacteria (Cyanophyta), like other bacteria, exist in one of three states:
a slimy community called a "biofilm", a singular free-floating "planktonic"
form, and a dormant "ultra-micro bacterium" (UMB).

When cyano-bacteria can't get enough food, they shut down and shrink to
one-third their normal size as a UMB. They can exist this way virtually
forever, floating around or buried. When they again encounter food, they
convert back to the planktonic form. When there are enough bacteria floating
around, and plentiful food, they group together, clamp to a surface, and
trigger genes that make a slimy covering. Bacteria in a biofilm are hidden from
predators, 500 times more resistant to antibiotics, and the film acts as a net
to catch food.

So, a few thoughts of my own:
You may be able to starve away the slime, but the bacteria will still be
dormant in your tank.
You can kill it off with erythromycin antibiotic, but the more established the
slime, the more antibiotic it will take.
The cyano-bacteria gets started in a still part of the tank, where the UMB can
rest against food, like the rotting leaves of Cabomba growing in the dead
corner of your tank.
After it is now awake in your tank, it will tend to slime in places where other
bacteria flow by and can join the community, like a siphon tube or skimmer box.
And since it has a slime net, it can catch food from the water flowing by.

George Booth <> wrote in article
> James Francis Redfern ( wrote:
> > I have found that this bacteria is promoted by still water and plant decay.
> ... among many other things.  It is common to find BGA in wet/dry 
> filter skimmer boxes and siphon tubes, which don't qualify as 
> "still water" situations.  I don't think science knows for sure
> what causes BGA to crop up.  
> -----------------------------------------------------------------------------
> George Booth                         "Nothing in the world is more dangerous 
>             than sincere ignorance and conscientious

> Freshwater Plant Tank Technology     stupidity" - Martin Luther King, Jr. 
> -----------------------------------------------------------------------------


by (Paul Krombholz)
Date: Sat, 18 Jan 1997

>Here's my question:  Does the term "cyanobacteria" refer to the bluish
>color that we see in our aquariums, or does it mean something else?  Many
>of us believe that cyanobacteria are capable of fixing atmospheric
>nitrogen.  I haven't seen experimental evidence that this is true, but it
>sure looks that way from my experiences with my tank.  I'm wondering if
>cyanobacteria may produce internal toxins to make it taste bad or even make
>it poisonous, but if these toxins might be a by-product of nitrogen
>fixation (CN- anions, perhaps).  I'm further wondering if the presence of
>an easier to metabolize nitrogen source such as NH4+ or NO3- might reduce
>the ability to produce such a toxin, if it exists.

They used to be called bluegreen algae, but cyanobacteria is being pushed
as the better name because it draws attention to the fact that they are not
related to other algae, but are large, photosynthetic bacteria.  Some of
them have a bluish pigment in addition to chlorophyll.  There are some
species that can fix nitrogen, but the ones that take over aquaria are
usually varieties of Oscillatoria, which does not have heterocysts, and I
assume it does not fix nitrogen.  The cyanobacteria are well-known
producers of defensive chemicals.  I have found that when the light is cut
way back they become much more palatable to snails and get eaten up fairly
quickly.  I doubt that the toxins are a byproduct of nitrogen fixation.
Those species that do fix N do it only in specialized cells, called
heterocysts that have heavy walls and no chlorophyll.  The enzyme most
directly involved in splitting atmospheric nitrogen apparently can only
function when oxygen levels are very low, and the heavy wall around the
heterocyst may function to keep oxygen out.

Paul Krombholz                  Tougaloo College, Tougaloo, MS  39174
In Jackson, Mississippi, where we had some freezing rain this morning.   

Nutrient limitation

by "David W. Webb" <dwebb/>
Date: Wed, 10 Dec 1997

>Date: Wed, 10 Dec 1997 11:48:06 -0500
>If we _are_ talking about cyanobacteria, then yes, many of them can fix
>nitrogen.  I don't think you'll get any argument.  But they do not then
>make that nitrogen available to higher plants in any meaningful way.
>(except Azolla, which I mentioned before)

I've found that cyanobacteria do contribute organic nitrogen to the system.

The process involves the cyanobacteria rapidly consuming nutrients until
they become nutrient limited in some way other than nitrogen.  At this
point, they begin to die off and decay, contributing their nutrients back
to the system.

- --
David W. Webb           Texas Instruments
(972) 575-3443 (voice)
(214) 581-2380 (pager)

To get rid of blue green algae

by Shawn Young <srly.dont_want_no_spam/>
Date: Thu, 22 Jan 1998
Newsgroup: rec.aquaria.freshwater.plants

Morpheus Cornelius wrote:
> i have been told that erythromyicin can kill the beneficial bacteria in
> the tank along with the blue-green algae.

This is a contentious position. It is a possibility, but I've 
wiped out infestations of cyanobacteria (blue-green algae) using
erythromyicin with no ill effects, and no notable changes in
water quality. 

Others will likely argue against treatment. E.g. remove/block
direct sunlight incident on tank faces; minimize areas of no
current, increase oxygenation, etc. (which are good suggestions
as well), and the choice is, of course, yours. It _is_ always a 
good idea to explore other options first. Cyanobacteria doesn't
like current, and thrives in dead spots with lots of light
(e.g. just under the surface of your substrate on a tank face
with lots of direct incident sunlight; or on top of a lot of 
very stable, unmoving floating plants in a well-lit tank). If
working to battle the infestation by minimizing such conditions 
fails, medication may be in order.

I have followed recommendations to reduce lighting while treating,
performing water changes every other day and then increasing light 
and performing a serious water change afterwards. (Maraccyn packaging
suggests that no water changes are required if water conditions are
"ideal" - whatever that means. I believe that this may mean if 
Ammonia, Nitrate, Nitrite are all non-existant - e.g. established 
tank with healthy bacterial culture - in which case this is
probably true; but why risk it.)

I personally suggest eradicating this nasty stuff by whatever
means works for you. (Incidentally, I came across a nifty article 
on toxins in cyanobacteria, at 

which firms up my conviction that this sludge has no place 
coexisting with me or my fish.) I would also suggest that as much 
of the bacteria as possible be removed in advance of treatment, 
and again, do try to improve current throughout the tank - 
wherever plant growth or other obstructions create the dead spaces 
in which the bacteria thrives - in addition to any treatment.

Also, treatments from your LFS, etc., such as Maracyn are pricey.
e.g. I'm looking at a Maracyn package right now (from the days
when I knew no better) which contained 24 200mg erythromyicin 
capsules (veterinary grade) at $19.99 Canadian (+ taxes). I am also
looking at a bottle which contains the better part of its original
200 250mg tablets (also veterinary grade) obtained from the Walmart
pharmacy for ~$7.50 Canadian (no tax). Simply tell your pharmacists 
what the pills are for, and they will likely let you buy them 
without a prescription. (This is singularly ridiculous... a
"prescription" medication which may be purchased over the counter 
at any pet shop for a huge fee...) You have to fill in their 
little "veterinarian" book:-)

You then do some very simple math... it's still 200mg per ten 
gallons every 24 hrs for 5 days. I have had to treat for 7 days 
on one occasion (again, no ill effects), which I considered risky 
but the damn stuff wouldn't go away. On the other hand, it has 
never come back... Do not break off the treatment prematurely - 
that way leads to bateria resistant to antibiotics.

Crush pills with e.g. a small mortar and pestle, and dump into 
your inflow.



BGA Anecdote

by George Booth <booth/>
Date: Wed, 21 Jan 1998

We had a mild problem with blue-green algae growing below the gravel line along 
the front 
of our acrylic tanks.  I would suppose conditions there are good: light being 
channeled in via the plastic, no water movement, low oxygen, available 
(?). It seems more problematic where E. tenellus or E. quadricostatus roots get 
close to the front (waste products acting as nutrients?).  

In the past, I've used a sheet of styrene plastic (0.080") to scrape the glass 
in front of the gravel.  This "cleaned" the area but was not a long lasting 
solution. What was happening, I guess, was the BGA was being pushed down and 
behind the gravel in the front.  It has been growing back at increasingly 
rates. Recently, I would see 'green fingers' coming up from the bottom the day 
after it was cleaned and it would be back as it was in less than a week. 

I've adopted a new strategy that seems to be working well.  Noting that the BGA 
rarely came above the gravel, I thought maybe it didn't like oxygenated water.  
So I fashioned an "L" shaped piece of plastic out of styrene the the lower arm 
shaped as a slender wedge.  Now I can slip the wedge down to the bottom of the 
glass and pull the BGA up into the water column. It disappears quickly and has 
stayed away for a couple of weeks now. 

George in Sunny Colorado

Seachem Flourish Question

by Mark Fisher <Mark.Fisher/>
Date: Wed, 23 Dec 1998

>I had a question for you as well: Why did you think that the cyano 
>problem might be attributable to low nitrate levels? By cyano I 
>assume you mean the blue-green "algae"? According to Baensch Atlas 
>volume 2 pg 162, the blue-green algae aka cyanobacteria can flourish 
>in the following conditions:  strong sunlight, rotting substrate, 
>excess feed, too few water changes, overfertilization or _high 
>nitrate levels_. If you are having a cyanobacteria problem I suspect 
>one of the other conditions to be the cause since you report that the 
>nitrate levels are low.

Baensch really isn't a good reference for this subject.  Blue-green
algae can fix atmospheric nitrogen, so their dominance becomes favored
at LOW nitrogen levels, not high.  As I posted earlier, blue-greens are
favored when the N:P ratio becomes low (less than 16:1), while the
growth of diatoms and green algae are favored at high N:P levels.  Thus,
when P is in abundance and N is low, you can generally expect an
outbreak of blue-green algae.  

This has been known among phycologists for years--I have a reference,
from a peer-reviewed journal, stating this back in 1979, and it has been
replicated by many others since.  Strong sunlight doesn't cause a
blue-green outbreak, either, nor does a rotting substrate.  Blue-greens
do not benefit from H2S, or CH4.



Seachem Flourish Question

by "Roger S. Miller" <rgrmill/>
Date: Wed, 23 Dec 1998

On Wed, 23 Dec 1998, Greg Morin wrote:

> One advantage with Flourish is
> that the nitrogen source is in the form of amino acids which are
> utilized as preferentially as ammonia is and even if the amino acids
> are broken down by bacteria, it is broken down in to ammonia first
> which can be utilized by the plants as well.

My reading doesn't confirm the idea that amino acids can be used directly
by plants.  I suspect that if this is true the ability to use amino acids
is going to depend very sharply on which acid you're talking about.  Can
anyone else confirm/deny this assertion?

> I had a question for you as well: Why did you think that the cyano
> problem might be attributable to low nitrate levels? By cyano I
> assume you mean the blue-green "algae"? According to Baensch Atlas
> volume 2 pg 162, the blue-green algae aka cyanobacteria can flourish
> in the following conditions:  strong sunlight, rotting substrate,
> excess feed, too few water changes, overfertilization or _high
> nitrate levels_. If you are having a cyanobacteria problem I suspect
> one of the other conditions to be the cause since you report that the
> nitrate levels are low.

I'll horn in on this, too.

I think we see two different kinds of cyanophyte occurences in tanks.  The
one that is described above is found mostly in neglected tanks. Under
those conditions, the cyanophytes tend to grow explosively, pose a serious
nuisance, and threaten to smother all of the plants in a tank.  The
infestation also rebounds very quickly (in a single day, for instance)
after it is mechanically removed.

Cyanophytes are also found in slow-growing patches and films, usually in
out-of-the-way places.  When the patches are mechanically removed they
recover relatively slowly (say, over the period of a week or two) and
don't threaten to smother the plants. This infestation isn't normally much
of a nuisance but if you don't do something about it, it can slowly
increase in size until it does become a problem.  This can happen in
well-maintained tanks and it's probably this sort of infestation that is
found at low nitrogen levels.  At least some cyanophytes are capable of
fixing nitrogen; at low concentrations of ammonia and nitrate most algae
growth is surpressed, so the cyanophytes can grow with less competition
for other dissolved nutrients - notably phosphorus.

In either case, the cyanophytes are probably competing successfully under
conditions with a low N:P ratio, which is consistent with the findings
that Mark Fisher paraphrased a few days ago.  In the first case the high
nutrient levels allow rapid growth; in the second case the low nutrient
levels allow only slow growth.

Roger Miller

In Albuquerque, pondering the fine line between intellectual synthesis and
sheer speculation.

Cyano Preliminary Results

by Mark Fisher <Mark.Fisher/>
Date: Tue, 5 Jan 1999

> Given that Neil can identify our normal cyanophyte plagues as probably
> Oscillatoria or Lyngbya, can anyone produce a study indicating that
> Oscillatoria and/or Lyngbya are capable of fixing nitrogen?  
> I think our
> oft-repeated statement that low nitrogen levels or low N:P 
> ratios promote
> cyanophyte outbreaks is based partly on the factoid that some 
> cyanophytes
> can fix nitrogen.  I'd like to see more specific information.

Nitrogen fixation is sensitive toward oxygen, so much that it can be
considered as a strictly anaerobic process.  However, some blue-green
algae have developed a special cell called a heterocyst, which is
nonphotosynthetic, does not produce oxygen, and has a thick cell wall
which prevents oxygen from diffusing in.  These blue-greens can fix
nitrogen in an aerobic environment, and will form more heterocysts in a
low-nitrogen environment

There are three basic kinds of nitrogen-fixing blue-green algae:  1)
filamentous heterocystous species, 2) some unicellular, nonheterocystous
species, and 3) some filamentous, nonheterocystous species.  The
nonheterocystous species can only fix nitrogen under hypoxic conditions,
so I think we can assume these species do not fix nitrogen in our
aquaria, at least not in the water column.

That leaves us with the heterocyst-bearing species as potential
nitrogen-fixers in our aquaria.  Oscillatoria and Lynbya do not possess
heterocysts.  However, Anabaena sp., which is a common component of
blooms, does possess heterocysts.



Black BGA in plantless tank

by krandall/
Date: Tue, 12 Jan 1999

Kelly Beard wrote:

>This may be considered off-topic, but it's about pseudo-algae.  I have what
>I think is BGA growing in my 26 gallon tank, but there's a difference.  The
>stuff is black.  Not dark green, but black.  It is easy to remove with a
>siphon.  I am going to experiment with this tank and try Maracyn.
>Anybody seen black BGA before?   Very unsightly.

Cyanobacteria comes in many colors.  Ever see the bright red stuff that
grows in marine tanks?<g>  I have dark maroon-bordering on black
cyanobacteria that coats the waterfall in my paludarium.  It's been there
for years.  I used to fight with it, worried that it would move into other
sections of the tank.  It doesn't  This species seems to NEED to be in the
highly oxygenated effluent of the filter.  I figure it helps extract more
nutrients on the way down.<g>

Oh, back to the main point.  Yes, Maracyn will kill it.  The reason that
doesn't work in my paludarium is that there are so many cracks and crevices
of damp rock where the cyanobacteria can retreat and wait for another day.

Karen Randall
Aquatic Gardeners Association

Cyano Preliminary Results

by Neil Frank <nfrank/>
Date: Sat, 02 Jan 1999

>From: "Adam R. Novitt" <>
>Subject: Cyano Preliminary Results/long
>As you may or may not be aware I've been doing some research on 'green
>water' or Cyanobacteria.

The title of this survey may be a bit misleading. While some green water
_can_ be caused by Cyanobacteria (unicellular species of blue green algae),
there is also green water from green algae, dinoflagellates, golden and
yellow-green (incl. diatoms),etc. Wetzel says most BG are filamentous, but
most planktonic BG are members of one family -the coccoids (e.g. Anacystis,
Gomphosphaeria and Coccochloris). If the water is green and smells bad,
then BG is a candidate. BG algae including the first 2 mentioned are very
sensitive to copper. Thus, people who have a moderate amount of copper in
their water may be less prone to these and other algae.

If BG algae is the suspected culprit, a small dose of Erythromycin might be
an antidote. It might be interesting to test a small amount in a gallon jar
with a proportional amount of mycin (~20mg). I don't advocate erythomycin,
but have used it to get rid of oscillatoria and lyngbya (the stuff which
forms sheets).

>1. When did the bloom occur?   .....This would indicate to
>me that an elevated ambient or water temp can be a factor in establishment
>of the bloom.  

This may not necessarily make sense for BG algae -- BG blooms in nature
occur in autumn (because of change in nutrients)... but still might be a
factor because of increase metabolism. Coincidentally, I just had a "green"
water explosion in my 125g tank after treating it for ich and raising the
temp from 76 to 85 deg F. Actually, the water wasn't green, but the tank
was not a cystal clear as it way before. I got rid of the algae by running
a diatom filter for 4 hours. It was nice to see the hazy appearance
disappear as the tank got progressively cleaner and more constrasty.
Sometimes, the diatom powder will become coated with a brilliant green
color and after it stops running, the water in the filter will be a
beautiful bright green. This time, however, the coating was golden
brown.... indicating a different type of algae.

> Some contacted
>me to say they'd kept planted tanks for decades and never once had the
>"aquatic clap" and it must be the unseemly habits of the less virtuous
>aquariest that brought it on.  

I have been keeping planted tanks for over 3 decades and have had green
water for the same amount of time.  Despite all my experience and
knowledge, I even seem to see it more over the last 10.... but I also keep
more planted tanks now.<G>  Green water might be avoidable if aquarium
conditions are perfectly stable. This is one of the reasons that new tanks
may get it. However, I am not perfect and sometimes it occurs from abuse
(e.g. stiring the bottom which introduces some phosphate ladden
particulates into the water column), or when plant growth slows due to
neglect of one thing or another (e.e. less frequent water changes).


Antibiotic Treatment of Cyanobacteria

by "Roger S. Miller" <rgrmill/>
Date: Sun, 17 Jan 1999

On Sun, 17 Jan 1999, Karen Randall wrote:

> You are certainly right that you need to treat long enough to kill all of
> whatever organism it is you are trying to kill.  I would maintain, however,
> that in my experience, Cyanobacteria _is_ completely killed within the two
> treatments.  I have never had a recurrance after a treatment (except in the
> case of the water fall, which is for different reasons which I have
> explained)  There are certainly a number of types of infections where the
> medical community has found that a shorter treatment period is effective
> than previously thought. (UTI's and ear infections are two types that I
> know of)

The cyanobacteria are normally reduced to a less-than-visible population
within less time than the treatment requires.  Perhaps not wiped out but
certainly reduced to a point where it doesn't rebound in the short term.
But the cyanobacteria in the tank aren't the only microbes that are being
treated by the antibiotic.  Any initially erythromycin-sensitive microbe
in the tank is effected by the antibiotic and could gain resistance from
the repeated use of the antibiotic.  Use of reduced strengths of the
antibiotic is likely to further encourage the development of resistance by
systematically selecting stains that have started to develop resistance.

I don't question the therapeutic effect of short-term treatments for human
ailments, but remember that it was the medical use and overuse of
antibiotics that lead to the development of resistant strains in the first
place.  More recently, the widespread agricultural use of antibiotics has
been implicated.

> Do you have any evidence that resistant forms of Cyanobacteria have
> developed as a result of a full strength two day treatment with Maracyn?
> The reason I specifically _like_ the use of erythromycin for Cyanobacteria
> is that it is already a fairly useless drug for fish diseases.

I haven't heard of any erythromycin-resistant strains of cyanobacteria.  
To that extent the warnings about developing resistant strains are
theoretical, so can you can accept or reject the idea as you see fit.

Also, I don't know what the consequences of erythromycin resistance would
be.  In medicine, as resistance to one strain develops the industry has
just moved on to the next available alternative.  They're running out of
alternatives.  In aquarium keeping we would just move on to another
antibiotic.  I think.  And I hope there are no other resistent pathogens
developed while we do it.

The actual chance of a resistent strain of anything developing in my tank
or in your tank are very slim, but there are millions of aquarists all
over the world and if they are carelessly dosing their tanks with
antibiotics then resistent strains will develop somewhere.

(No Title)


Roger Miller


by "Chuck Lawson" <lawson/>
Date: Sun, 17 Jan 1999

>Subject: Re: Aquatic Plants Digest V3 #782
>SCAYUGA writes:
>>     I am presently treating a 20L planted aquarium for a BG algae
>>  I caught it before it carpeted the tank and am doing the five (5) day
>>  dose Maracyn treatment.

>Bob Dixon Replies
>Why only half-doses?  The folks who invented the stuff did numerous tests
>see what is effective.  THey did not double the dose requirement just to
>more money.

De-lurking for a moment or two here; this sentiment might be in the right
place for some aquarium products, but it certainly isn't for erythromycin.
The makers marketed this for years as the best thing since sliced bread when
in reality it's never been proved to be effective on any fish disease other
than a few specific conditions (kidney infections, if I recall correctly)
among salmonids.  Since most of us don't keep trout or salmon in our
aquariums, it wasn't good for much for the home aquarist other than wiping
out the biofilter making whatever problem was being treated that much worse.
It's a reasonably safe bet that most any "cure" anyone experienced was a
result of either a) coincidence or b) doing the water changes recommended as
part of the treatment regime.

The only saving grace of the product is that some marine people accidently
found out a few years back that it was good for cyanobacteria.  Since the
package directions obviously weren't related to any real studies involved in
curing aquarium fish, and the package dosage is reasonably well-known to
severely inhibit biofilters, using as little as possible to get the job done
killing BG algae seems like a good idea.

(A little background; the value (or lack thereof) of Maracyn was beaten to
death on Compuserve's FishNet back in the early 90's...  Mardel had a bit of
a fit, but never refuted the information, as I recall... There's been a lot
of water over the overflow since then, so my memory may be a little hazy.)

- - Chuck

Erythromycin and breeding pairs?

by "Maladorno, Dionigi {DRUG~Nutley}" <DIONIGI.MALADORNO/ROCHE.COM>
Date: Fri, 16 Apr 1999

Marie-Andree Lemieux wrote: <<< Erythromycin and breeding pairs?
last summer I nuked the blob using Erythromycin successfully.
It is now back but I have breeding Rams in my thank and another one with a
Discuss breeding pair.
I would like to know if any of you have treated tanks including breeding
fish with Erythromycin and if the fish were ok. I was worried it might make
them sterile. (maybe a stupid worry but... don't want to take a chance).

If your intention is primarily to breed, it could be a good idea to
give up the erythromycin treatment. I do not think it would affect
fertility, but it would cause some extent of stress to the fish and 
the biofilter, without removing any of the causes of Cyanobacteria
For breeders, large and regular water changes are a must, which
would be the most correct approach to the b/g problem.
Some algae persisting despite good water changes are actually quite 
liked by newborn fry, since they harbor lots of microorganisms they like 
as first food.

Dionigi Maladorno
This message presents personal opinions which are not necessarily those
of my employer.

Beating back bluegreen algae

by "Roger S. Miller" <rgrmill/>
Date: Wed, 25 Aug 1999


Several years ago I read an interesting text called "Environmental
Microbiology".  I think it was there that I found the statement that blue
green algae are essentially ubiquitous in nature but rarely dominate the
environments where they live.  The cases where bluegreen algae do dominate
are those where conditions are so extreme that green algae and plants
cannot thrive; e.g. high nutrient levels, low nutrient levels, high
temperatures, low temperatures and so on.

On that basis it's always seemed to me that when bluegreen algae comes to
dominate a planted aquarium there must be something extreme about the
conditions in the tank that are unfavorable to the growth of plants and
green algae.  The natural extension to that thought is that bluegreen
algae in an aquarium could be controlled or eliminated by promoting the
more moderate conditions that favor plants and green algae.

About this time last year one of my 10 gallon tanks developed an
infestation of bluegreen algae.  The tank is lit with 2 15-watt
flourescent tubes (3 watts/gallon) and choked with Vallisneria.  It also
housed some C. wendtii and an algae-covered bit of driftwood that I'm
rather fond of, a few male common guppies, an oto, some ghost shrimp and a
female American flag fish. The tank was unfiltered but circulation was
provided by a small powerhead.  I fed very little to encourage the fish to
eat algae.  The bluegreen scourge started out slowly but after a few
months I was cleaning off the driftwood and the Val every week and
siphoning the bluegreen slime off the bottom.  I had no particular plans
for the tank so I let things go along like that.

A few weeks ago I decided to use the tank to grow out some Barclaya
longifolia seedlings, so I needed the bluegreen algae out of there.  
Instead of nuking the tank with antibiotics I decided to try a more
natural cure.

I started changing conditions in the tank not so much to discourage the
bluegreen algae as to encourage the growth of green algae and plants.  
The changes took several weeks.  First I thinned out the Val and planted
some E. tenellus in the tank (variety is good).  Then I started feeding
the fish more heavily to increase the nitrogen and phosphorus supply.  
Finally I started using a commercial aquatic plant fertilizer and added
yeast-generated CO2 from a 1-quart generator.

The growth rate of the bluegreen algae declined only slightly and things
remained pretty well unchanged until I started the CO2, then the pieces
appeared to fall together abruptly.  The bluegreen algae didn't disappear
suddenly but it did cease to grow and start disappearing.  I gave the tank
a fairly thorough going over last weekend when I changed water and removed
what I could.  What was left after the cleaning is nearly gone now.  The
tank is almost complete free of bluegreen algae.

I've tried similar cures a couple times before.  I've sometimes even gone
to the extent of triggering a green water bloom.  As Dave Whittaker
pointed out recently, green water combats many other types of algae.  
That seems to include bluegreen algae.

The method is pretty simple.  Don't try to kill the bluegreen algae.
Instead, combat it by encouraging the growth of competing plants and green
algaes.  Identify extreme conditions and fix them - give your plants the
best chance to fend for themselves.

Roger Miller

Battling BGA

by George Booth <booth/>
Date: Wed, 2 Aug 2000

Many people seem to think that water circulation is one of the keys to 
eliminating BGA. Based on anecdotal evidence, I would discount that. Our tanks 
have trivial amounts of BGA and it occurs in the trickle filter skimmer box 
(water swirling and cascading around) and the trickle filter siphon tube (!). If 
good circulation ("water movement") prevents BGA, these two areas would be the 
last places I would expect to find it. 

In the past we *have* noticed BGA forming among dense floating plants and at the 
interface between the glass and front gravel, leading to a suspicion that BGA 
likes areas of no water movement. But is seems like it must be something else. 
Perhaps an area rich in nitrates (or some form of nitrogen) combined with high 
light might be a cause. Areas on the surface would have access to atmospheric 
oxygen, especially in the skimmer where lots of mixing is possible and it is 
close to the lights. The area in the gravel near the glass might have high 
nitrates due detritus caught there and little circulation to remove it. The 
glass can channel light down there making it also pretty bright.

Just some thoughts, little real data.  

George Booth in Ft. Collins, Colorado ( 

Up to Algae <- Plants <- The Krib This page was last updated 17 February 2002