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Green Water


  1. Green water... Remedied! (Story)
    by (The Admiral) (31 Oct 1993)
  2. Green Water (was Re: Forget hatching brine shrimp).
    by (Patrick White) (Tue, 5 Jan 93)
  3. Diatom filters & algae blooms
    by "Dan Resler" <> (Mon, 9 Oct 1995)
  4. Control of green water with Daphnia
    by krombhol-at-felix.TECLink.Net (Paul Krombholz) (Thu, 21 Sep 1995)
  5. Green water fallacies?
    by "David W. Webb" <> (Thu, 23 May 1996)
  6. Green Water and Newbie Questions
    by krandall/ (Tue, 28 Oct 1997)
  7. Ideas, please
    by krombhol/ (Paul Krombholz) (Mon, 27 Oct 1997)
  8. Plants - sound the death march.
    by Dave Gomberg <gomberg/> (Wed, 03 Dec 1997)
  9. Green Water (QYNGA?)
    by Erik Olson (e-mail) (Thu, 18 Dec 1997)
  10. Green Water
    by "Dixon, Steven" <stdixon/> (Thu, 18 Dec 1997)
  11. Yet more green water!
    by krandall/ (Tue, 02 Dec 1997)
  12. Green Water Update
    by MP <pearlsco/> (Mon, 08 Dec 1997)
  13. Green Water
    by krandall/ (Fri, 19 Dec 1997)
  14. Green Water / BGA
    by MP <pearlsco/> (Wed, 26 Nov 1997)
  15. Green Water
    by "M. Pearlscott" <pearlsco/> (Fri, 19 Dec 1997)
  16. Newbie question #3: Algae control
    by Steve Pushak <teban/> (Thu, 05 Feb 1998)
  17. Green Water
    by Neil Frank <nfrank/> (Fri, 06 Mar 1998)
  18. Green Water (was Re: Forget hatching brine shrimp).
    by patbob/ (Patrick White) (Tue, 5 Jan 93)
  19. Aquatic Plants Digest V3 #647
    by Julius Odian <uodiaj00/> (Sun, 15 Nov 1998)
  20. Vortex vs. System 1.
    by krandall/ (Mon, 16 Nov 1998)
  21. green water
    by krandall/ (Thu, 19 Nov 1998)
  22. Green water
    by Steve Pushak <teban/> (Sat, 21 Nov 1998)
  23. Green water
    by ac554/ (David Whittaker) (Sun, 22 Nov 1998)
  24. Green Water and Hydra
    by "Merrill Cohen" <amc2/> (Thu, 17 Dec 1998)
  25. green water hell
    by "Roger S. Miller" <rgrmill/> (Thu, 17 Dec 1998)
  26. green water
    by "Roger S. Miller" <rgrmill/> (Wed, 18 Nov 1998)
  27. B.O.D. and green water
    by krombhol/ (Paul Krombholz) (Sun, 22 Nov 1998)
  28. Cyano Preliminary Results
    by Neil Frank <nfrank/> (Tue, 05 Jan 1999)
  29. my exerpience w/green water
    by "emilio" <emilio/> (Fri, 28 Apr 2000)
  30. different green water
    by "Roger S. Miller" <rgrmill/> (Sat, 29 Apr 2000)
  31. Re:Can't get green water????
    by krombhol/ (Paul Krombholz) (Wed, 10 May 2000)
  32. Nitrates/green water/test kits (question)
    by krombhol/ (Paul Krombholz) (Sat, 19 Aug 2000)
  33. Green water issue
    by Thomas Barr <tcbiii/> (Fri, 20 Oct 2000)
  34. green water
    by Michael Eckardt <mike/> (Wed, 18 Apr 2001)
  35. Green water: a cause?
    by Thomas Barr <tcbiii/> (Fri, 20 Jul 2001)

Green water... Remedied! (Story)

by (The Admiral)
Date: 31 Oct 1993

Some of you may recall reading my post, "Green Water Remedies" last
week. It detailed my plight to rid my water of the horrible cloudiness
that overtook it during antibiotic treatment of diseases beginning
on 10/5. By Friday the water was so bad you couldn't see fish 2" away
from the glass.

I consulted numerous sources for advice and came up with four possible
remedies: Light starvation, chemical treatment, diatom filtration, and
UV sterilization.

Being rather out of funds, but afraid to kill off my higher plants, I
initially opted for "chemical treatement" over the light starvation
method. Well, I got some Aquarium Products "Algae Destroyer Liquid"
and put in the appropriate amount. No reaction. So after that, I
added some Petcetera "Acurel F", once again without a reaction.
Getting rather pissed off I did something rash. I called TFP
(800-733-3829) and they turned out to be very nice and have the
best prices of the places I surveyed (Daleco and Pet Warehouse
were the others). I was going to buy either a Diatom filter or a
UV Sterilizer. Either one would run me $60-80, so the price made
me indifferent. I decided to go with the UV/Powerhead combo because
it would require less maintence (bulb change every 1000 hours vs new
filter poweder after each use). So I ordered an Aquanetics 8WT Mounted
UV Sterilizer, Aquaclear 402 Powerhead, and 2' of 5/8's tubing for
all of $77.61 including shipping (only $4.41).

This came in via UPS on Friday, 10/29, five days after the failed
experiment with the chemical treatment. Majorly excited (I always like
"high tech" stuff) I immediately rinsed the whole stuff and installed
it. Not having a UGF and not having ordered their powerhead prefilter,
I made one out of some filter sponge foam I had lying around. Hooked
the baby up (this stuff was serious overkill for my 20H) and set it
running at 5PM. I smashed up my thumb while I was at it so couldn't
go out flying that night, so settled on a night of hanging out and

Got back around 11:45 or so. Water still hadn't cleared- indeed it
was worse than it was 5 days ago (it was like that not due to the
UV sterilizer, though- it was bad before then). Being a bit buzzed
(indeed one may even say drunk) I added another 60 drops of this
"Acurel F" to the tank while a friend and I watched. 

This was the most amazing sight I have ever seen in my Fishkeeping

I was drunk enough not to believe what I said, so I handed my journel
to my friend and told him to write all about it. This is what my entrys

10/29 500P 77/76 [that's the internal/external thermometer temperatures]
           Installed UV Sterilizer & Powerhead. Bashed thumb.
      1152P 60 drops Acurel/F 
      [At this point my friend took over]
      - Clearing up in front of my fucking eyes!!!
      - It's 1200AM, 10/30/93 I can see everything! It's unbelieveable.
      The filter is completely clogged with algae. Blows Doug's mind.
10/30 12:07 Perfectly clear!!! Amazing what money can buy
      - Doug is drunk. He can't write. 

In any event, the biobags need changing really bad- they're the brightest
green I've ever seen green be.

I was simply amazed. My thoughts on the matter:

Acurel/F does exactly what it claims to do! Amazing stuff!

However, it does not work on LIVING algae. You have to kill it first,
e.g. with the UV Sterilizer, then add it. The filter will then take care
of the rest.

TFP is a good place to shop. Their catalog is excellent, too! It's bigger
than an issue of FAMA or TFH.

Fourteen minutes from couldn't see 2" to perfectly clear. Amazing.

Just FYI, here is my tank setup:

20H, Whisper 3, UV sterilzer & powerhead detailed above
Whisper pump & fine bubble airstone
Two strip lights, 15W triton & 15W cheapo
5 cardinal tetras, 4 zebra danios, 4 cherry barbs, 2 gold barbs
1 sunburst gourami, 1 algae eater, 1 horse-faced loach
CLEAR WATER, moderately planted

I plan to run the UV sterilizer only a few hours a day. At 240
gals/hr from the powerhead, it should cycle the water plenty
if I run it but one hour.

Anyone have any comments?



PS: I'm proud of my first "informational" posting as opposed to a
"give me information" posting. With experience, I may even match
up to Oleg someday. :)
Doug Fields, PP-ASEL, IA-Student, N1NJN
Yale University,  (203) 436-2966  voice

Green Water (was Re: Forget hatching brine shrimp).

by (Patrick White)
Date: Tue, 5 Jan 93
Newsgroup: alt.aquaria

In article <> pjs-at-gvgdsd.GVG.TEK.COM (Peter J. Stonard) writes:
>Anyone know the secret to truely green 'soup'??

	Quickest way I saw to make it:

	Put in a fish that eats algae.  Add nutrients (fish will probably do
that for you).. adding some phosphate might be good too.  Add light (at least
a cool white, better light for a better bloom).
	Fish eats all algae sitting still, which favors the single-cell type as
the only type that can bloom (and not be eaten).

	I found this out by accident.. added a P* to suck up all the algae
coating the tank walls and had a really thick green soup in a couple weeks.

Pat White (, work: (503) 578-3463)

Diatom filters & algae blooms

by "Dan Resler" <>
Date: Mon, 9 Oct 1995

Just a follow-up on my previous question ... as Karen said, diatom
filters do indeed remove suspended algae. I bought a Vortex diatom
filter and put it to work on a 35g with pea-soup water. And <presto>
.... clear water within 15 minutes (leaving the filter bag a very
satisfying bright green color). I raised the MH pendant, cut back the
timer to 8 hours, temporarily suspended using the Dupla drops, and
the bloom has yet to return (after 5 days). We'll see.

It was an intesting situation - no algae on the plants or glass (thanks to
SAEs, black mollies and a *wonderful* farlowella) yet water so full of
algae you couldn't see the back of the tank. A first for me!

Control of green water with Daphnia

by krombhol-at-felix.TECLink.Net (Paul Krombholz)
Date: Thu, 21 Sep 1995

>Sep 21 10:47:00 1995
> From:       ''                               (BNR400)
> Subject:    Green Water Control with Daphnia
>Anyone out there tried to control algae bloom in your plant tanks
>using one or several of the Daphnia species? It would seem to be a
>very natural approach, as the Daphnia population would increased
>quickly with increased algae bloom, and correspondingly decrease with
>algae consumption.
>You couldn't have many fish (except algae eaters), but then fish
>aren't crucial to a planted tank.

I have controlled green water with Daphnia many times.  I normally grow my
plants without fish, but I have some tanks with fish.  I find that I have
to take all the fish out, even Corydoras catfish.  The Daphnia multiply
rapidly and clear up the green water.  I don't think it is a good idea to
return the fish immediately.  Wait a few weeks or months and let the plants
get well established, even to the point of being a bit crowded.
Reintroduce the fish gradually.  The tank should stay clear.  On some
occasions my daphnia have not multiplied and cleared up the green water,
and I have always found that adding nutrient solution makes the green water
become brighter green, and then the Daphnia start multiplying.  Apparently,
if deficient in nitrogen, and possibly other nutrients, the algae doesn't
have enough nutrition to allow the Daphnia to multiply.  I have seen this
requirement for additional nutrients perhaps a dozen times, and the Daphnia
have always responded to the addition of nutrients and done their job.  I
even worked out a kind of 'Daphnia cage' that can hold Daphnia in a tank
with fish and protect them from the fish.  The water circulates through the
cage and the Daphnia can keep it clear while you have fish in the tank.  I
did an article about the Daphnia cage in The Aquatic Gardener a few years

Paul Krombholz                  Tougaloo College, Tougaloo, MS  39174

Green water fallacies?

by "David W. Webb" <>
Date: Thu, 23 May 1996

>From: (G.Tong)
>I've got another question for you all. Someone on the Goldfish List has
>stated firmly that green water is caused by incomplete biological
>filtration, that if our filters were working, there would never be green
>water. His reasoning is that green water algae can only live when there is
>ammonia around whereas "hairy algae" (his term not mine) can thrive on
>nitrates and phosphates. He claims this is why green water is *never* found
>in planted tanks.
>Neither his conclusion nor his assumptions along the way sound right to me.
>Advice? TIA.

I would agree if he said that green water would cause incomplete nitrification
by bacteria, primarily because suspended algae are very effective at
out-competing the bacteria for nitrogen.  

Perhaps he came up with this conclusion by either adding a UV sterilizer to the
tank or diatom filtering and then finding out that his bio-filter wasn't at a
high enough capacity to handle the ammonia production.

However, from what I've seen, green water usually reduces NHx and NOx levels in
the tank to basically zero in a very effective manner.  The biggest problem
I've heard of then is when someone kills the suspended algae quickly enough to
add the nitrogen back to the water while overloading the bacterial
nitrification system.

David W. Webb
Enterprise Computing Provisioning
Texas Instruments Inc. Dallas, TX USA
(214) 575-3443 (voice)  MSGID:       DAWB
(214) 575-4853 (fax)    Internet:
(214) 581-2380 (pager)  Text Pager: Subj:PAGE:David Webb

Green Water and Newbie Questions

by krandall/
Date: Tue, 28 Oct 1997

Paul wrote:

>To get rid of persistant green water I net out my
>fish and add Daphnia.  After they clear the water, I keep the fish out for
>several months longer, allowing the plants to grow more.  Then, when I
>return the fish, the water has always stayed clear for at least a year. 

>Another low tech solution is the Daphnia cage, a cage of monofilament
>polymer cloth where the mesh size is just small enough to keep Daphnia from
>getting out.  The water circulates through, and the Daphnia clear out the
>algae but are protected from the fish.  It works quite well for me and
>requires very little upkeep.  See TAG 5:3, pp 50-54 for an article on the
>Daphnia cage.

Paul, a friend of mine maintains a number of aquariums in commercially.  He
has one that he recently took over that had a terrible green water problem.
 Obviously in this instance, removing the fish wasn't an option that would
be popular with the client.  He had done a series of water changes to
reduce nutrient levels, and had diatomed the tank several times.  Each
time, the tank looked good when he left, only to green up again quickly.  

He was discussing the problem with me, and I mentioned that you had had
some success confining daphnia in a net within a fish tank.  Since he sells
net style breeder traps in his store, I suggested that he throw some
daphnia in one of those and give it a try.  What could it hurt?

Within a week, the tank was crystal clear.  He then moved the daphnia back
to their tub at the store, and the the tank has remained clear with no
further problems.

For a more "high tech approach, I have another friend who maintains a 600+
gallon planted tank in a restaurant.  The owner insists on running the
lights from 8AM until 12 midnight.  As a result, the tank was plagued with
green water.  My friend was running multiple diatom filters on the tank
continuously, and changing them at least twice a week to keep the tank
presentable.  He finally resorted to the pond solution of buying a UV
sterilizer.  The tank cleared quickly, and he now only needs to run it
intermittently to keep the problem at bay.  

I think this solution is overkill in most applications, but it might be of
use to someone with else with a really big tank that needs to be lit for
long periods in a display situation. (public aquariums come to mind)

Ideas, please

by krombhol/ (Paul Krombholz)
Date: Mon, 27 Oct 1997
To: Aquatic Plants List

Roger Miller wrote Mon, Oct 27:
>I'm looking for plants that will coexist in unfertilized, very brightly
>lit tanks with val. americana, hornwort and crypt. wendtii.  The water has
>very little general hardness, but plenty of carbonate hardness and I've
>measured the pH in the tanks over 9.  Soon (when the leaves finally fall
>outside) these tanks will be getting about 6 hours/day of direct sunlight,
>and they each have 2 15-watt flourescent tubes with soon-to be upgraded
>reflectors.  Over the last couple years I've tried java fern, anubias nana
>and a myriophyllum sp. with varying degrees of miserable failure.
>I want to get enough growth in these tanks to put up some significant
>competition with the green water.  Alternatively, can anyone think of any
>(available) filter feeders that will live with grass shrimp, guppies and
>otos?  One tank has a clam in it already - clams do so-so, but I haven't
>been able to keep them alive more than about 9 months or so.

One possible filter feeder is the tadpole of the African clawed frog,
Xenopus.  They clear up green water fairly well, but, unfortunately, they
soon turn into frogs.

If green water is the major problem, then maybe the solution is a denser
growth of the plants you already have.  I would try to get more of the val
established.  Hornwort isn't very effective in clearing green water, even
when the tank is  packed with it.  Val, I think, is better.  Najas is also
a plant that grows well under high light, low CO2 conditions.  So is Egeria
(Elodea).  Perhaps some of the swords can also duke it out seccessfully
under these conditions.  To get rid of persistant green water I net out my
fish and add Daphnia.  After they clear the water, I keep the fish out for
several months longer, allowing the plants to grow more.  Then, when I
return the fish, the water has always stayed clear for at least a year.  My
planted tanks with any fish at all tend to have a rather low ratio of fish
to plants.  The higher this ratio gets, the better the chances for green

Another low tech solution is the Daphnia cage, a cage of monofilament
polymer cloth where the mesh size is just small enough to keep Daphnia from
getting out.  The water circulates through, and the Daphnia clear out the
algae but are protected from the fish.  It works quite well for me and
requires very little upkeep.  See TAG 5:3, pp 50-54 for an article on the
Daphnia cage.

Paul Krombholz in chilly, Jackson, Mississippi, where we are forcast to get
our first frost tomorrow morning.  

Plants - sound the death march.

by Dave Gomberg <gomberg/>
Date: Wed, 03 Dec 1997
To: apisto/

At 11:28 PM 12/2/97 -0800, Wright wrote:
.>Now, if someone can tell me how to not *kill* my green-water cultures,
>I'll be a happy man. 

Aha, finally a chance to help Wright.  OK, set up a kiddie wading pool and
throw in a few tablespoons of dry dog food.  Wait a  month.  Result:  All
the green water you can use.  That is my recipe for growing white clouds in
bulk, too.

This is the apistogramma mailing list,
For instructions on how to subscribe or unsubscribe or get help,
Search for "Apistogramma Mailing List Archives"!

Green Water (QYNGA?)

by Erik Olson (e-mail)
Date: Thu, 18 Dec 1997

> From: "Mike Lehman" <>
> I went to the archives and the FAQ and read all about green water.  It has
> been talked about quite extensively.  Unfortunately, many of the ways to get
> rid of green water are opposites.  Some recommend doing nothing and waiting,
> others recommend varying the light source (some up, some down), still others
> suggest varying the nutrients (some suggest too few, some too much).  Others
> recommend introducing daphnia (I am having a hard time finding out what it
> is and where to get it).  I have a population of snails (they must have come
> with the plants).  Hair algae does not seem to be as much of a problem.

I beleive green water in the tank is one of those things caused by
imbalances, and will eventually go away if there is a proper balance of
nutrients, light, plants and filtration.  The suggestions are basically
different approaches to speeding this up, and fall into the categories of

  1) limiting a crucial factor that the algae is consuming
  2) increasing a crucial factor that allows the plants to outcompete the
     algae for the remaining factors
  3) physically removing the algae until the tank re-balances.

Decreasing light or various nutrients falls under (1), and increasing
light or nutrients (essentially the PMDD thesis!) falls under (2). Daphnia
is the equivalent of an algae-eating fish for green water, and covers (3).
In order to try (1) or (2), you probably should know your conditions well.
(3) will not be a permanent solution unless your plants adjust to the
tank conditions.

You know, now that I look at it, the above paragraphs can basically apply
to any algae plague. 

Daphnia, btw, are water crustaceans, and can sometimes be harvested from
ponds.  Usually, you can get them from other hobbyists who culture them
for food.  They must be kept in a tank with no fish or other predators, or
they will not be able to reproduce (which is key for eliminating the
algae).  When they have elminated the algae, however, they make a great
hi-protein dinner for your fish.  

  - Erik

- ---
Erik Olson				
eriko at

Green Water

by "Dixon, Steven" <stdixon/>
Date: Thu, 18 Dec 1997

Mike Lehman wrote: >>>I have a 55 gal setup that is 3 weeks old.  I have
a 175 watt MH light on 12 hours per day.  I have CO2 injection with PMDD
added.  My plants have been in for about 1.5 weeks and are growing very
well.  My problem is green water.>>>

I've just come out of a green water problem quite successfully by
following Karen Randall's advice.  Two steps:  1.  Eliminate excess
nutrients in the water column (through water changes).  2.  Darken the
tank for 4 or 5 days (I used a dark blanket and duct tape and kept the
lights off the entire time feeding the rainbows once a day in the dark
- -- poor things!).  I opened the tank up on the evening of the 4th day
(no biblical pun intended <g>) and had pristine crystal clear water
which has remained clear ever since (about 2 weeks now).

A couple of other thoughts:  You have a brand new setup.  See the
archives on running-in a new tank.  We've just had a good discussion
which you should consider.  The (almost) universal advice is to use
nutrient supplements sparingly, if at all, during the early run-in
period.  You're asking for trouble if you add the full regimen of
supplements when the plants aren't sufficiently established to use those

One other observation:  My green water problem persisted for over a
month after I was 'certain' that there were few excess nutrients in the
water column.  FWIW, I also have bright lights as you do.  Practicing
'patience' after correcting the initial water condition did not
eliminate the green water in my case!  A 50% water change would be
almost clear.  Then a couple of days later a light green haze would
settle in (just a soft light pastel green, not green pea soup, as
before).  My guess is that the green water can hang around in fairly
good water conditions which in the first instance would not support an
outbreak of green water.  This is where the blanket comes in.  The
higher plants can handle a few days of darkness without any apparent
signs of distress (at least my plants seemed to do quite well).  The
green water, on the other hand, could not handle the darkness.  It was
wiped out. (Unlike young Luke Skywalker, my green water DID see the
power of the Dark Side! <g>)

Good luck and let us know what you do and how it turns out.  Green water
is an interesting adversary. Steve Dixon

Yet more green water!

by krandall/
Date: Tue, 02 Dec 1997

>I do belive that I offered a possible cure for bacteria bloom, initail
>questiom was in regards to running in a new tank.  If I erroniously
>stated it was a cure for green water I apologise.  Within the context of
>the discussion though I belive it was clear that it was "green water"
>(should this be called white water?) due to tank run in.  I have never
>actually experienced true algea bloom so I can't say much about it. 

Just so you don't confuse them again, "green water" is green.  The
bacterial bloom that sometimes is associated with NTS is whitish.  It has
no green color to it because it is not algae.  A product that introduces
more nitrifying bacteria into the tank may hasten the end of a bacterial
bloom.  But then again, patience will work just as well and is less expensive.

Green Water Update

by MP <pearlsco/>
Date: Mon, 08 Dec 1997

I stated a couple of weeks ago that I believed when Nitrogen became a
limiting nutrient, that this can allow for the production of green water
(unicellular algae).  I still believe this, but have an addition.  If
one allows potassium (K) to become limiting, this will also alow green
water.  My thinking is this...

I suggested that one could eliminate green water by the addition of
Nitrogen to the system.  This is true, but ONLY if potassium is
constantly present.  In my tank, I had great green water for a few
weeks.  I decided to try to eliminate it, and started adding nitrogen. 
This worked great for a few days, then it stopped clearing.  What I
hadn't realized is that I had then caused the potassium to be the new
limiting nutrient.  Once my brain realized that, additions of potassium
and nitrogen cleared the tank in two days.  No joke... two days.

The source of nitrogen I used was KNO3 (potassium nitrate), and for
potassium I used K2SO4.

By dosing with both of the above, I shifted the balance to having
Phosphorus being the new limiting nutrient, and knocked out the green

Hope you all found this experiment as interesting as I have.



Green Water

by krandall/
Date: Fri, 19 Dec 1997

Steve Dixon wrote:

>I've just come out of a green water problem quite successfully by
>following Karen Randall's advice.  Two steps:  1.  Eliminate excess
>nutrients in the water column (through water changes).  2.  Darken the
>tank for 4 or 5 days (I used a dark blanket and duct tape and kept the
>lights off the entire time feeding the rainbows once a day in the dark
>- -- poor things!). 

Just a couple of notes.  While, of course, any excess nutrient problem
should be corrected before darkening the tank, the main reason for a BIG
water change just before wrapping it is to remove as many algae cells as
possible from the tank.  If you kill off huge masses of algae in a tank, it
may overload your bacterial filter.  The bacterial activity may reduce O2
to levels that are dangerous to your fish.

I would prefer not to feed the fish at all during this period.  The fish
can easily go a week without food if they are well fed and in good health
before the beginning of their "fast".

Karen Randall
Aquatic Gardeners Association

Green Water / BGA

by MP <pearlsco/>
Date: Wed, 26 Nov 1997

Okay... I must bite at this one (again).

I wasn't thinking too straight when I replied to Steves post originally,
but let me straighten things out now.  I first need to agree with
Roger.  Green water is related to iron, but only as all plants need iron
for growth.  Right there is where I must differ in opinion.

Green water seems to grow, but only when the conditions favor it over
other plants.  In aquariums where nitrate is the limiting nutrient, and
phosphate is in excess, green water (unicellular algae) does great. 
Both can be un-measurable by test kits, and here is why:  With nitrate
being limiting, this asserts that everything else is present in larger
quantities.  Phosphates only need to be in slightly higher quantities. 
They can still be below test-kit range be being used up as soon as
nitrate becomes present, even in the most minute amount.  In addition to
a constant presence (however low) of phosphates, the depletion of
Nitrates puts the higher plants at a disadvantage.  Higher plants are
better at competing when nutrient levels are more "balanced".

So now knowing that having nitrate being a limiting nutrient supports
green water growth, it is easy to eliminate it without filters,
additives, medications, etc.  Just add nitrates to the tank (KNO3 works
well).  By SUSTAINING a low level of nitrates (3-5ppm) in the tank, you
force the nutrient balance to shift.  This will cause phosphates to
become limiting.  Given time, this will cause the plants to thrive and
green water to fail.  Be patient, as it does normally take a little
bit.  A lot does depend on how turbid the green water is, how many
plants you have in the tank, how much you fertilize (and what you
fertilize with), and the bioload of the tank.

This would also explain why some tanks just seem to "automatically fix
themselves."  Here I would suggest that the biomass has contributed to
rising levels of nitrates, causing the balance shift I talked about.

- -----
- ------
Complication, Depression and Stress have the power to put one on the
right track of life.

Green Water

by "M. Pearlscott" <pearlsco/>
Date: Fri, 19 Dec 1997

I've written a bit about green water in the past few months, but seeing
how I don't really like to search the archives unless I have to, I'll just
give a quick remedy.

I find that green water appears in tanks that are either K or N limited.
By having one of these the limiting nutrient, that means that P is always
present.  The way to eliminate green water is to shift the balance and
cause P to be limiting.  You can do this by adding N (easily obtainable as
KNO3), and adding K (available as K2SO4).

With the addition of both, green water should disappear in relatively
quick order.  I would guess under one week.  Mine went away in two days
once I realized that K was limiting.

Any questions, feel free to email me personally.


- ------
The more people I meet, the more I like my plants...

Newbie question #3: Algae control

by Steve Pushak <teban/>
Date: Thu, 05 Feb 1998
Newsgroup: rec.aquaria.freshwater.plants

Olga Betts wrote:
> It
> doesn't look nice to us but plants and fish don't mind green water at
> all.

The fish don't mind at all and the plants won't mind too much however
the green water is going to absorb most of the nutrients in your
aquarium water very quickly so don't expect the plants to grow much
while you have it. Test your nitrates to verify this next time you get
green water and you may get a surprise: Zero nitrates!

Some folks combat green water by increasing one nutrient (K or N) which
may be in short supply which allows the plants to suck up the remaining
nutrients which may be in excess (P, Fe).

Another strategy is to reduce the length of light or intensity. This
often may be enough if its not caused by a severe excess of nutrients.

Another way is to black the tank out for a few days. This kills the
green algae fairly well but it can re-occur because you haven't removed
any nutrients from the system or changed anything else like lighting. It
can also create a high oxygen demand from the dead algae so you may need
extra aeration.

My preferred method is to use a micron filter which can get your water
sparkling clean. This has the advantage of removing the nutrients in the
bio-mass of the green water.

The coolest method of all has to be setting up the tank without fish at
all and using daphnia to eat the green water. You'll have a tank full of
daphnia in no time. When you want to grow daphnia, you will be surprised
how hard it is to get a tank of green water!! There is also a way to
keep daphnia in a fine net cage which passes the green unicellular algae
but retains the daphnia. This is described in one of the back issues of
The Aquatic Gardener (TAG)journal in an article by Paul Krombholz called
"The Daphnia Cage". See my web page for a link to the AGA site where you
can order back issues of TAG or better yet, join the Aquatic Gardeners
Association and order the complete set of back issues!! A fantastic
reference in my most humble opinion!

Related to this idea is the use of filter feeding shrimp. I keep such
shrimp but I don't experience problems with green water very often (i.e.
only when setting up an overly fertile substrate or in my early days). I
don't know if it would really work well but I'd like to hear from folks
who've tried it. There are other filter feeding critters like freshwater
clams, that might do the trick but they tend to starve in the long run
because of a lack of food (so I hear).

PS. NEW aquatic plant pictures to go up on my website very soon!! (maybe
tonight but probably by the weekend) These are my best ones yet but
there is another batch in processing which should be even better.

Steve Pushak 

Visit "Steve's Aquatic Page"
 for lots of pics, tips and links for aquatic gardening

Aquatic Gardeners Association

Green Water

by Neil Frank <nfrank/>
Date: Fri, 06 Mar 1998

>From: "Dixon, Steven" <>
>Subject: Green Water
>Noel Llopis asked about a persistent cloudy water problem.
>My comment applies only to 'green water.'  
>Darkening the tank with a dark blanket for 4 days knocked the green
>water out completely -- the water was sparkling clear -- and it has
>remained so for about 4 months now.  If you think your problem is a
>green algae bloom, give it a try.  It has worked for several of us.

When I get a green water bloom in anything bigger than a 10-15gal tank, I
use my SYSTEM ONE diatom filter.... the greatest aquarium appliance since
the development of the all glass aquarium. This filter is self priming,
filters out the suspended algae and other micron size particles in
minutes... when concentrations are high, the flow will slow and a second
application may be needed... sometimes I let it run the second time for an
hour or so to really clear the water column.   I also run mine after I
disturb the substrate to instantly remove any suspended clay particles and
avoid getting an algae bloom. This takes the worry out of playing in the
tank <g>. The water becomes sparkling clear and the plants immediately
start to pearl O2.

Neil Frank, AGA

Green Water (was Re: Forget hatching brine shrimp).

by patbob/ (Patrick White)
Date: Tue, 5 Jan 93
Newsgroup: alt.aquaria

In article <> pjs-at-gvgdsd.GVG.TEK.COM (Peter J. Stonard) writes:
>Anyone know the secret to truely green 'soup'??

	Quickest way I saw to make it:

	Put in a fish that eats algae.  Add nutrients (fish will probably do
that for you).. adding some phosphate might be good too.  Add light (at least
a cool white, better light for a better bloom).
	Fish eats all algae sitting still, which favors the single-cell type as
the only type that can bloom (and not be eaten).

	I found this out by accident.. added a P* to suck up all the algae
coating the tank walls and had a really thick green soup in a couple weeks.

Pat White (, work: (503) 578-3463)

Aquatic Plants Digest V3 #647

by Julius Odian <uodiaj00/>
Date: Sun, 15 Nov 1998

>Date: Sun, 15 Nov 1998 09:22:33 -0600
>From: (Paul Krombholz)
>Subject: Re:fluidized bed filters and green water
>Has anyone ever had green water while using a fluidized bed filter?  I am
>wondering if being passed through all those moving sand grains would kill
>planktonic algae cells.

I have used a fluidized bed filter namely and Lifeguard FB300 on a 55
gallon tank and have had green water. In fact that tank had more different
forms of Algae than I have experienced in any other tank, but I don't think
the they are related events. The only thing you got to make sure with
fluidized beds is that the water is well areated after it leaves the

So in short no, I haven't found it to help.


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Vortex vs. System 1.

by krandall/
Date: Mon, 16 Nov 1998

>Although I have not personally used a System 1 filter, I can say that a
>Vortex, properly primed, will clean any aquarium up to 75g in an hour, not
>4hrs.  It may take 4hrs to clear a larger tank such as a 125g or 150.  This
>is before even adding any of their special 'superchar' carbon, in which
>case, the tank would clear even faster.  Vortex filters will also last you
>at least a decade.  And, for $58 bucks for the smaller one from that fish
>place, if you have green water, this is the filter to get.  You can purchase
>diatom powder from a local pool retailer store for about $7 for a 10lb bag.
>The 'superchar' carbon you must purchase from the company, but the small
>container they sell will last you easily 10 years.  

I also use a Vortex diatom filter which I've had for many years.  It does
do an _excellent_ job.  The problems are that it's hard to start up, is
tippy and made of glass (a bad combination!<g>) and not easy to move from
one tank to another.  That said, it has been a real work horse through the

I've seen the System 1 filter in action, and it is easy to start, hangs on
the edge of the tank, works at least as well as the Vortex and can be moved
easily between tanks.  It's more expensive, but at least to me, the utility
justifies the added expense.  My only problem is that the danged Vortex
just keeps working (I use it very infrequently) and I can't justify the
expense of a replacement.  When it _does_ go, I will definitely replace it
with a System 1.

BTW, I also own, use and like a HOT Magnum.  But I use it as a small
canister filter which drives a CO2 reactor.  Used in this capacity I have
no complaints.  I probably would not buy another, just because I like the
Magnum 350's so much and have mostly larger tanks.  I don't think I'd
bother "wasting" either of the Magnums as an intermittent polishing device.
 Knowing me, It would be put into service as a full time filter on some
tank or other, and that would be the end of it.<g>  I'm kind of surprised
how many people feel they need a polishing filter with any regularity.
It's probably been 2 years since mine saw any service, and I could probably
count the number of time I've used it in total on both hands.  Do many
people really need to use a polishing filter with any regularity?  I find
that my tanks stay crystal clear (let's not get into blue bucket debates
again... they look very clear when viewed through the tank the long way)
without any heroic measures.<g>  Even after a water change, glass cleaning,
mulm removal session, any residual cloudiness will be gone within an hour,
and this is with minimal filtration on the tanks.

Karen Randall
Aquatic Gardeners Association

green water

by krandall/
Date: Thu, 19 Nov 1998

Steve wrote:

>One reason you probably can't test any nitrates or phosphates in the
>green water is that they are in the biomass of the algae. The algae are
>continuously being consumed and the nutrients recycled. What you want to
>happen is for the nutrients to become locked up in the macrophytes, the


>This is also why, if there aren't sources of nutrients (ie decomposing
>material), then flocullating and filtering the algae is a good way to
>remove those nutrients from the system! Better than shutting off the
>light because that kills the algae but doesn't remove the nutrients. The
>plants, even in the dark, are still dutifully absorbing nutrients.

Yes, but you leave even one cell behind, and it quickly multiplies again.
Unfortunately, many "green water" organisms thrive under exactly the same
conditions where our higher plants thrive.  That's why the best approach,
IMO, is to reduce the amount of suspended algae in the water column, (use
whatever means you like... I prefer large water changes because there are
other benefits, but use flocculants and/or micron filtration if you prefer)
 THEN black out all light to the tank for 5-7 days.

One last thing about green water:  It's not dangerous, just annoying.  And
it tends to go away eventually even if you do nothing.  I think lots of
people try lots of different things.  In the midst of their scurrying
around, eventually the green water "disappears" one day.  They attribute
this disappearance to whatever remedy they tried last.  It might have been,
but it's just as possible that it was ready to disappear on its own!<g>

Karen Randall
Aquatic Gardeners Association

Green water

by Steve Pushak <teban/>
Date: Sat, 21 Nov 1998

Paul Krombholz did a lot of experiments with green water and adding
nutrients including nitrate and these are written up in TAG 4:2 and 5:2.
According to Paul's data adding nitrate doesn't do anything but make the
green water greener. I'm afraid I can't go along with the suggestion
that green water is _caused_ by a shortage of nitrate. It results when
conditions are favourable for the algae to grow.
- -- 
Steve Pushak                              Vancouver, BC, CANADA 

Visit "Steve's Aquatic Page"
 for LOTS of pics, tips and links for aquatic gardening!!!

Green water

by ac554/ (David Whittaker)
Date: Sun, 22 Nov 1998

Steve Pushak wrote...

>Paul Krombholz did a lot of experiments with green water and adding
>nutrients including nitrate and these are written up in TAG 4:2 and 5:2.
>According to Paul's data adding nitrate doesn't do anything but make the
>green water greener.

This is false. He says that he added Hoagland's Solution several
times to deal with the nitrate deficiency. Both the algae and the
plants got greener. Eventually the plants gained the upper hand.
I quote the first three sentences of the second article.

"About the fourth or fifth time I added Hoagland's Solution, an
interesting thing happened. The tank cleared up. It didn't happen
immediately, but over a period of about two weeks."

Maybe Paul would care to comment, since he wrote the two-part
article. It's actually an interesting little piece.

> I'm afraid I can't go along with the suggestion
>that green water is _caused_ by a shortage of nitrate. It results when
>conditions are favourable for the algae to grow.

Did someone suggest that green water is caused by a shortage of
nitrate? Roxanne left her tank unattended for a month. Who knows
what nutrients were or were not present. In any case the green
water got a foothold. Tanks with green water which I have tested
for nitrate have measured low to zero. Those on the list who
have green water might wish to perform the test.

Conditions favourable to the establishment of green water are
bright light and a pH>6.0. I cannot recall a case of green water
in a well-planted aquarium with large fish, only in those filled
with guppies of various sizes. Is this observation shared by
others on the list?

In his article Paul wrote that the disappearance of the algae
may have had more to do with plant mass and the number of filter-
feeding critters it was able to support. As plant mass increased,
so did the number of animals consuming planktonic algae.
Eventually they were able to clear the water.

This might explain why Roxanne's aquarium developed the green
water. As the hunger of the fish increased, they would have been
driven to searching out smaller prey including those creatures
which feed on the suspended algae. The system was thrown off
balance. The result was an algae bloom.

I have three tanks side by side with identical lighting. One is
pea soup. Maybe I'll perform a green transfusion to a healthy
tank in order to see if the problem corrects itself.

- --
Dave Whittaker

Green Water and Hydra

by "Merrill Cohen" <amc2/>
Date: Thu, 17 Dec 1998


Stop changing the water!  Every time that you do this, you give the dying
"green water" a "shot in the arm"!  Continue with the "Crystal-Clear" with
no water changes; and, if possible, get some Hornwort and put it in the

Hydra -- (someone else) -- Get "Clout" and follow directions -- it won't
hurt the plants or fish!

Merrill Cohen

green water hell

by "Roger S. Miller" <rgrmill/>
Date: Thu, 17 Dec 1998

On Thu, 17 Dec 1998, Roxanne Bittman wrote:

> I wrote about one month ago that I had a green water
> problem after a one month vacation.  It cleared up
> briefly after a couple of 25% water changes plus the
> addition of Kent's Pro Clear.
> However, it came back!  Despite water changes and
> Pro Clear, it returned.  It's mad now too, because
> NOTHING I do is getting rid of it.  What I have tried:


I recall that I had a green water problem (now gone) that started around
the same time as yours.  I used a flocculant and ran a Magnum 350 w/micron
filter over night to clear the water.  That worked, but the green water
rebounded to the cloudy-but-not-real-green stage for about three weeks
running.  I was out of town over Thanksgiving weekend and when I returned
the water was as thick as it ever was.

The green water is now completely gone.  I used daily focculant treatments
(with Hagen P Clear) and ran the Magnum w/micron filter continuously for
several days in a row, changing and cleaning the filter each day.  I also
suspended all fertilizing and reduced fish feedings.

Reducing the fertilizing and feeding probably slowed the phytoplankton
growth rate, and the continuous filtering kept the water clear for a
continous period of time.  I think that the clear period let the rooted
plants (and unfortunately some blue green algae) accelerate their growth
and take over from the phytoplankton.

I have left the tank unfiltered now for two weeks and the water is still
crystal clear.  I haven't returned to my previous fertilizer routine - I'm
looking for convenient and inexpensive ways to replace foliar fertilizing
with substrate fertilizing because green water is a recurring problem in
this tank.  The blue green algae that expanded briefly when I was running
the filter is now in a gradual retreat.

I imagine that our green water problems are as unique as our aquariums, so
this expience may or may not be of any use.  This worked for me, good luck
with yours.

Roger Miller

green water

by "Roger S. Miller" <rgrmill/>
Date: Wed, 18 Nov 1998

Roxanne Bittman wrote:
> What is really interesting about this is the variety of
> methods used to clear up green water, all of which
> seem to work, under at least some conditions.

I thought this very interesting, too and I think it reflects on the
complexity of the problem and on the diversity of our aquarium-keeping

> What else is curious is that, the day I posted my
> question, I returned home to the green tank, changed
> 25% of the water, added no fertilizer, added 2 capfuls
> of Kent's Pro Clear (a flocculent, tho' apparently not
> the best, see below) and three hours later, the tank
> was crystal clear.  Not just better, but eye-poppingly
> clear.
> I was surprised, since I had done exactly this set of
> things twice before, with no such result.  I must have
> hit a threshold of nutrient lack and low algae (Euglena,
> I am told) population, so that the flocculent did its job.

This is somewhat like my first experience with Hagen's flocculent "P
Clear".  The evident difference being that my first application had some
effect but left the tank still cloudy.  The second application worked
perfectly.  I reasoned that there was so much algae in suspension during
the first treatment that the flocculent got "used up" before it effected
all the algae. The second time there was less algae there and enough
flocculent to handle it all.

There are a lot of different planktonic green algaes and cyanophytes that
might cause green water.  That diversity could be one reason why Roxanne
got so many different answers about how to clear up the problem.  Euglena,
for instance, can't use nitrate as a nitrogen source but most other plants
and algae can.  Adding nitrate would feed everything in the tank *but* the
green water and hand the competitive edge back to the plants.  Other
people have reported that fine filters alone will pull down green water
blooms, but that didn't work for Roxanne and it didn't work for me.  The
failure would be explained if the algae species that didn't filter out had
a smaller cell size than the algae species that could be filtered out.
Adding a flocculent overcome's the cell-size problem.

In my tanks I get green water mostly when I do something that slows down
the growth of the plants without reducing the light or nutrient levels.
That's usually heavy pruning, thinning or replanting.  When the plants
slow their growth the single celled algae are the first ones to take up
the slack.

I suspect that other people have similar experiences; green water blooms
happen when something slows the plant growth or there's a sudden increase
in the light or nutrient availability that shakes up the balance.  The
wide range of solutions reflects the many different "balance points"  that
different aquarists maintain and the many different ways that the tanks
can get knocked off from and returned to their balance.

Roger Miller

B.O.D. and green water

by krombhol/ (Paul Krombholz)
Date: Sun, 22 Nov 1998

A few more things about BOD:
(1) The BOD determination does not indicate directly the amount of organic
matter in the water.  It merely gives you the rate of oxygen consumption.
There may be a lot of organic matter that is very refractory to
decomposition, and, therefore, you may only record a small BOD.  On the
other hand, there may be a smaller amount that can be decomposed by
bacteria easily, and that may give you a larger BOD.

(2) If you suspect, or if you find out, that there is such a large BOD that
the oxygen content drops down to zero during the five days, you must dilute
your sample with deionized or distilled water in order to get an accurate
determination.  You can try a 1/2 dilution and a 1/4 dilution, for example.
Suppose your 1/4 dilution drops from 7 ppm to 4ppm over the five day
period.  The BOD would then be (7-4)*4, or 12 ppm.

I didn't know they were providing bacteria these days to seed the sample.
We always just used the bacteria that came along with the local waters when
I was doing BOD's.  Maybe you need these seed bacteria when you are not
using natural stream, lake or aquarium waters, but making up various
mixtures of water and organic matter.

Steve Pushak wrote:

>Paul Krombholz did a lot of experiments with green water and adding
>nutrients including nitrate and these are written up in TAG 4:2 and 5:2.
>According to Paul's data adding nitrate doesn't do anything but make the
>green water greener. I'm afraid I can't go along with the suggestion
>that green water is _caused_ by a shortage of nitrate. It results when
>conditions are favourable for the algae to grow.

After a number of the nutrient additions, the green water did go away in
that experiment, but I think it went away because the plant (Eigeria densa)
got large.  I don't know why the green water went away when the plant got
large.  It could have happened because of allelochemicals or because (my
favorite hypothesis) the large surface area of the plant provided
attachment sites for organisms feeding on green water, or some other reason
I can't think of.  I don't think the plant was superior at competing for
nutrients, because it didn't show any signs of being superior when it was
smaller.  I had enough light so that I don't think that the plant shaded
out the green water algae.

Paul Krombholz, in cool, sunny, central Mississippi

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Cyano Preliminary Results

by Neil Frank <nfrank/>
Date: Tue, 05 Jan 1999

>From: "Dixon, Steven T. (Exchange)" <>
>Subject: Cyano Preliminary Results/long
>First and foremost, green water and cyanobacteria are completely
>different animals. <G>  What we refer to as green water is not bacteria
>at all, but unicellular algae.  Karen pointed this out last week,
>apparently to no avail. 

Green water and cyanobacteria are not necessarily different. Some "green"
water _can_ be caused by unicellular species of cyanobacteria (blue green
algae). The blue green algae that we usually think about is Oscillatoria
and Lyngbya (the stuff which forms sheets). But there are also planktonic
blue green algae. According to Wetzel, these are mostly members of one
family -the coccoids (e.g. Anacystis, Gomphosphaeria and Coccochloris).
Cyanobacteria come in a range of colors including green and blue-green.
Here is a nice microscopic picture of unicellular stuff... and it looks
green to me.

I checked another reference (Smith, Fresh Water Algae of the United
States). This is what he says about Microcystis (=Anacystis): "Microcystis
is essentially a planktonic genus and one that often causes 'water blooms'
in hard water lakes."  I have also read elsewhere that planktonic algae can
cause the water to appear green or brown.


my exerpience w/green water

by "emilio" <emilio/>
Date: Fri, 28 Apr 2000

I just wanted to relate my experience with the method of covering a 
tank full of green water.  Mine was positive.  I had green water 
after about 2 or 3 weeks of being set up (120gal, 440watts).  
Stopping the fertilizer (Schoeler's Natural Gold) made it go away a 
bit, but once I started fertilizing again it came back heavier.  I 
didn't want to spend the money on a Micron filter, so I did a number 
of 50% water changes to no avail.  So I decided to do a 95%(!) water 
change and then cover the tank in complete darkness for 5 days.  For 
the past 2 weeks since I uncovered it, it's been crystal clear.  And 
I've started to fertilize again for the past week, but only at 1/4 
the recommended dose.  I'm planning to increase that little by 
little.  My biggest mistake was not realizing that Natural Gold 
relies on fish food & waste to provide nutrients that aren't in the 
fertilizer.  My only non-plant inhabitants were algae eaters (ottos, 
SAEs, yamato shrimp).  So, as soon as I uncovered the tank I went to 
the store and bout some tetras. :)

Hopefully things will remain clear.  Many thanks to this list and its 
active participants.

Emilio Ramirez
(at work with my car full of recyclables waiting to get dropped off)

Ideas? Appointments?  FREE SANITY with email, personal calendar, to-do-list, GRATIS!

different green water

by "Roger S. Miller" <rgrmill/>
Date: Sat, 29 Apr 2000

On Sat, 29 Apr 2000, Jon Hammond wrote:
> Any other ideas.. also any other ideas to get rid
> of it (filter the water through floss, (can't afford diatom), lights out for
> 5 days (will this hurt my plants / fish).. Any ideas would be great.. thanks
> ! :o))

Seasonal changes in ambient light seem to set my tanks up for a bout of
green water.  There's a period in November when natural light falling on
one of my tanks increases because of the lower angle of the sun.  At that
time even small disturbances (usually a heavy pruning) will result in
green water.  Perhaps in your tanks an increase in ambient light plus the
introduction of a few new fish was sufficient to trigger the green water.

To clear up green water I add a flocculent, then filter through floss.
The flocculent, incidentally, seems to plug my Magnum 350's micron filter
cartridge, so filter floss is actually the preferred filter medium.

Jon went on to write:
> Anyway from my point
> of view I think that green water, given some time will die out by itself.
> Being an algae it multiples preety much expotentially and goes through
> phases... after the expotential phase it peaks and then without any more
> nutrients crashes... ie no more algae...

I've tried waiting out green water episodes before and it doesn't seem to
go away on its own.  The sequence of exponential growth - level out -
die off is typical of growth in batch culture.  What I see in my green
water blooms is something like exponential growth leading to thick green
water, then a slight decline in the thickness of the green water to a
green-but-not-quite-so-green state that seems capable of lasting

Roger Miller

Re:Can't get green water????

by krombhol/ (Paul Krombholz)
Date: Wed, 10 May 2000

Lynn wrote:

>.....Green water...some of us are plagued with it, and some of us can't get it
>I am trying to culture daphnia, but can't seem to get my water to turn green.
>Just goes to show you how picky algae can be too!

Just keep guppies, goldfish, or some other "messy" fish, feed them well,
light the tank with about 3 watts per gallon, and have no plants in the
tank and no filter.  If that setup doesn't produce an endless supply of
green water, I would like to know your secret.

Nitrates/green water/test kits (question)

by krombhol/ (Paul Krombholz)
Date: Sat, 19 Aug 2000

- ------------------------------
David Brooks discussed his green water problems, To try to summarize,
filtering does not work; the green water comes back.  He plans to try
duckweed, next, then a Daphnia cage in the filter.

Daphnia cages work, but they are tricky to set up and you have to worry
about what type of screening you use.  They can work without any forced
water movement through them, but they should take up perhaps 10% of the
volume of the tank, and you have to have some snails inside and outside to
keep the screening from plugging up with algae.  Avoid window curtain
material!!  It is made of nylon threads, and these threads are made of very
many woven smaller threads.  The total surface area of nylon exposed is
great, and someting toxic is given off that will stop growth in your plants
in about a month and kill them by two months. This production of toxic
material will continue for years.  It is probably something released from
slow bacterial decompositin of the nylon.  Monofilament screens are safer.
If you have a current through the Daphnia cage, it should be a slow one or
else all the Daphnia will be pinned against the screening, and they can't
survive that for very long.  Daphnia cages work, but they require care and
patience.  Another possibility would be to have another tank nearby with
Daphnia and circulate the green water through this tank with an appropirate
filter to keep the Daphnia from being carried into your fish tank.

Water sprite seems to be better than several other plants I have tested in
keeping down green water.  Credit for the claim that water sprite is
exceptional, goes to Richard Sexton.  I did some experiments with different
plants to see how crowded they became before the green water went away.  In
the case of Hygrophila polysperma, Ceratophyllum demersum and Eigeria
densa, the tank had to become densely packed with the plant before the
green water went away.  I mean, packed so much that the resident guppies
had a hard time getting up to the surface to get at their food!  However,
with the watersprite, about half the tank could be open with light reaching
the bottom, and almost all the green water was gone.  There was only a
slight haziness.

For a quick but expensive solution to green water, try pumping the water
through an ultraviolet sterilizer for about four days.

Paul Krombholz, in hot, dry, central Mississippi

Green water issue

by Thomas Barr <tcbiii/>
Date: Fri, 20 Oct 2000

One bad thing regarding the blackout method for getting rid of Green
Your plants are all thin and shoot for the surface during this time. It's
alright for some plants but if you have a nice tight low patch of Gloss it
looks like crap afterwards.
Tom Barr 

green water

by Michael Eckardt <mike/>
Date: Wed, 18 Apr 2001

If you have green water, go look at the archives from about a year ago.
Guess what? Green water stories. I have been following the APD since
inception, and green water issues come up regularly in the spring.
Why is that? Is it the additional photoperiod? A change in water composition
(spring run offs)? Increased airborne algae spore count? Who knows.
It would be interesting to plot the geographic distribution of the recent
outbreaks to see if there is a common link. Are the northern regions more
affected than the south?  What's the experience in tropical regions? etc.

I guess this would make a nice little research project for an

Michael Eckardt, Waterloo, Ontario

Green water: a cause?

by Thomas Barr <tcbiii/>
Date: Fri, 20 Jul 2001

One thing I have noticed in a number of tanks and in my own twisted
experiments with this alga(e) is that it is almost always accompanied by a
disturbance in the N cycle of a tank with a spike of NH4+ appearing in
almost every single case. Reasons for the NH4+ spike are many.

1)New tank-poor N cycle, not established yet

2) Filter removal, a spike since bacterial action has been removed/reduced.
We often see in non filtered tanks that slight haze or a continual issue in
high light no filter tanks.

3) Massive uprooting, removal of a small tree like sword plant etc (see
bacterial disturbance again). Messing too much with your tank in some way.

4) Nutrient removal-stunted plants not taking up NH4+ production and no time
for the bacterial responses. Turn off CO2 all of sudden, No NO3 etc. That
stops the NH4+ uptake that's taking place so it builds up slightly and
triggers the GW to propagate.

5) Other factors such as good growth then poor CO2 all of a sudden. Any
dramatic slowing of growth rates(hence less NH4+ uptake). Any event that
lets the NH4+ build up pretty much.

It seems that there a window of opportunity for GW that's in between the
bacteria getting it and the plants getting it. If care is taken to ensure
plants get fed well and that the bacteria have a good home as well(deep
sub's, wet dry filters, big canisters etc) this will minimize the outbreaks.

And water changes will remove build ups of NH4's so after a big hack, after
a long period of abuse, new tank set ups, good maintenance will take care of
your tank.

I do know GW water is not caused by: Most of the other nutrients. NH4+ is
the exception and the common issue in many experiences with to date. This is
how I induce it actually. I toss a couple of Jobes into the water column of
a very high light 20 gallon tank and it's there in a day or two. It will
live on little once it's there but seems to get "turned on" by the NH4
These tanks have good CO2, high light(where we often find GW in such tanks),
good everything as far the nutrients. I lowered the CO2 for a week, GW. I
shut off the filter, GW. I tossed in a ton of PO4, no GW. I tossed in a ton
of KNO3, no GW. I tossed in a ton of micro's, no GW. I did a big pruning and
removal without a water change after, GW. I added jobes, GW. New tanks by
the dozens, GW. 

It really a neat and very useful alga tool for us. It's easy to get rid of,
takes no effort and causes no real harm to the tank. But we can do all sorts
of things to it and it keeps coming back:)

FWIW, I have never had GW in any of my tanks. I had to induce it by adding
Jobes. I keep my tanks quite rich in everything but since the plants are
doing well there's little NH4+ around to be had. But I've been at work
lately checking this one out. I have some ammonium sulfate to play with to
see if it's definitely the NH4+ or not. Problem is I have to remove the
critters to do this in case I go overboard from ammonia poisoning:) But it
should not take much to trigger this event I suspect. Haven't killed things
prior with the lower amounts from Jobes, new tanks etc.
Tom Barr 



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