You are at The Krib ->Plants ->Fertilizer [E-mail]

Comments on Kevin and Paul's Paper

Algal control in the aquarium- Peter Hughes

Re: Algal control in the aquarium- Paul Sears

Re: Algal control in the aquarium- Kevin Conlin

Algal Control article and Phosphates- Neil Frank

Re: Algal Control article and Phosphates- Paul Sears

Sears and Conlin paper- Paul Bucciaglia

Re: Sears and Conlin paper- Kevin Conlin

Re: Sears and Conlin paper- Karen A Randall

PMDD Paper- David Whittaker

Re: PMDD Paper- Kevin Conlin

Re: PMDD Paper- Paul Sears

EDTA photodegradation- Paul Sears

EDTA photodegradation- Elizabeth Worobel

EDTA photodegradation- Franc Gorenc

KCl vs K2SO4- Neil Frank

Re: KCl vs K2SO4- Paul Sears

Later comments and related information.

From: Peter
Hughes peterh-at-pican.pi.csiro.au
Date: Wed, 3 Apr 1996 10:34:59 +1000 (EST)
Subject: Algal control in the aquarium 
Comment 1  Comment 2

Hello

I would like to offer a few observations and comments about the lengthy 
treaty that we just received on algal control. It was very interesting to 
see that someone has gone beyond conventional wisdom and tried something 
radical.

In the abstract it is mentioned that the micronutrients, N and K should 
be in slight excess of P to provide algal control. I can see that this 
may be true, but it should only be true if P then becomes limiting. If 
the general feeding strategy/fertiliser reserves are high in P then it 
will still remain in sufficient excess to cause problems.

I definetly agree with the statement about the lack of good information 
on what water quality perameters are able to be "tweaked" and also the 
important ones for impending trouble.

A word of caution should be exercised here because the tanks that are 
used as examples are exactly that. There are some problems with the 
testing that should be pointed out:
1. the tanks are individual tanks and have not been duplicated in any 
way. This may be seems a bit strange, but it is impossible to know if the 
tanks would have gotten over those same algal problems by themselves. 
This sort of experiment can probably only be carried out in a tank that 
is divided after an initial period of running in, with the same planting 
on each side. This is difficult to do but would give some valuable data in 
terms of the difference in plant growth and what the algal population 
differences are.

2. Repeated addition of P to the, supposedly, P limited tanks and careful 
observation of algal populations. Only by adding pure P over several 
succesive cycles will show the dependency of algae on P. The fertiliser 
tablets that remain undissolved in the substrate in case 2 may be 
providing some other nutrient that sets off the algal bloom and not 
necessarily P. The single addition of Phosphate and the resulting 
observations do give a pretty clear indication about what is going on, 
however it needs to be taken a bit further than it already has been.

So what do I think of this evidence, I think that it is very interesting, 
but stops just short of being proof. In saying this I am being a bit of a 
devils advocate, but so much aquarium information is not really good 
enough to be called fact (see recent discussions on the 
useability/unavailability of ironIII in aquaria as an example). I have 
started adding some K2SO4 to my tanks partly because of this discussion 
and partly because I think that I have a K deficiency.

I hope that the authors do not take this as personal criticism, it is 
not. I know how difficult it is to design experiments to prove something. 
Their evidence also fits with general information here in australia. Our 
soils are generally deficient in P and so that is the fertiliser that is 
used and it is runoff from those fields that causes our algal blooms.

Peter Hughes
ANGFA (ACT)

 

------------------------------

From: Neil Frank nfrank-at-nando.net
Date: Wed, 3 Apr 96 07:09:46 EST
Subject: Re: Algal Control article and Phosphates
Comment 1 

First, my compliments to Kevin and Paul for taking the time for their
careful observations and to write up their experiments. This is the best way
to advance the 'science' of aquaristics and to facilitate healthy
discussion. The one change I would suggest is to include some information
about the chemical testing, including their lower limits of detection. I may
have more suggestions later.

As said by Peter Hughes,<peterh-at-pican.pi.csiro.au>, I agree that the
conclusions are true only if P is really the limiting nutrient. It is
conceivable to me that adding N, K, S and trace elements could help push
growth to the point where one or more of the trace element might still be
limiting. Adding a 'balanced' set of te does not necessarily ensure this.
Without a control in the experiment or a sensitive chemical test of the full
spectrum of chemicals, we do not know for sure. Also as said by Peter, "but
it is impossible to know if the 
tanks would have gotten over those same algal problems by themselves."

Nevertheless, the hypothesis seems reasonable and I also subscribe to the
philosophy that adding N and K will cause something else to limit plant
growth - very possibly P. To support the alternative hypothesis -- when soil
(and possibly other materials incl.laterite) is used in the substrate, iron
and magnesium would be adequately available in the substrate (at least for a
while). Reducing their concentrations in the water column will also starve
algae.

Regarding the effect of P, there was an interesting article published in TAG
which is an English translation of one originally published in AquaPlanta
(see TAG, V7n1). The author, Peter Peterson, slowly reduced phospahte
concentration by adding a 0.3% solution of of iron chloride (over 8 day
period). He reduced the Phosphate concentration to 0.1 ppm. During this
time, he observed that some species of higher plants started to suffer and
algae bloomed. This suggests that his algae was able to utilize phosphates
at a lower level than some of his plants. He observes that the results may
be species specific.

With extra feeding he brought the conc back to 0.6 and deficiences vanished.
He concludes that a range of P concentrations may be optimal for good plant
growth without algae. He thinks that 0.2 ppm is too low. The article had
many other interesting obsevations about levels and different types of
aquarium plants and growing conditions. The above also supports Peter who
said "Only by adding pure P over several succesive cycles will show the
dependency of algae on P"


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


------------------------------

From: Paul Sears psears-at-NRCan.gc.ca
Date: Wed, 3 Apr 1996 09:03:45 -0500 (EST)
Subject: Re: Algae control

> From: "Peter Hughes (X)" <peterh-at-pican.pi.csiro.au>
> 
> In the abstract it is mentioned that the micronutrients, N and K should 
> be in slight excess of P to provide algal control. I can see that this 
> may be true, but it should only be true if P then becomes limiting. If 
> the general feeding strategy/fertiliser reserves are high in P then it 
> will still remain in sufficient excess to cause problems.
>
	I agree entirely, and I keep a small fish load (so far) partly
so that I _know_ almost everything that goes into the tank.
 
> 
> A word of caution should be exercised here because the tanks that are 
> used as examples are exactly that. There are some problems with the 
> testing that should be pointed out:
> 1. the tanks are individual tanks and have not been duplicated in any 
> way. This may be seems a bit strange, but it is impossible to know if the 
> tanks would have gotten over those same algal problems by themselves. 
> This sort of experiment can probably only be carried out in a tank that 
> is divided after an initial period of running in, with the same planting 
> on each side. This is difficult to do but would give some valuable data in 
> terms of the difference in plant growth and what the algal population 
> differences are.
>
	I would really like to do some well controlled experiments, but
lack of time, money and space make it a bit difficult.  If anyone else
wants to do experiments, I would be very pleased, and would like to
hear the results.
	I am, however, pretty confident that the algae would not have gone
away by themselves.  I saw two highly undesirable (apparently) steady states
that were changed by doing something different in my tank.  The current
state is much better, appears stable, and reacts predicatably to substrate
disturbances.
 
> 2. Repeated addition of P to the, supposedly, P limited tanks and careful 
> observation of algal populations. Only by adding pure P over several 
> succesive cycles will show the dependency of algae on P. The fertiliser 
> tablets that remain undissolved in the substrate in case 2 may be 
> providing some other nutrient that sets off the algal bloom and not 
> necessarily P. The single addition of Phosphate and the resulting 
> observations do give a pretty clear indication about what is going on, 
> however it needs to be taken a bit further than it already has been.
>
	I agree.  I'm waiting for a while before I make any more P additions
to my tank, because I'm still pretty sure that there is a fair bit in the 
substrate. (effect of disturbance)  These effects are getting smaller,
however, as one would predict, and when they become _very_ small I shall
add controlled amounts of phosphate to see what happens.
 
> So what do I think of this evidence, I think that it is very interesting, 
> but stops just short of being proof. In saying this I am being a bit of a 
> devils advocate, but so much aquarium information is not really good 
> enough to be called fact (see recent discussions on the 
> useability/unavailability of ironIII in aquaria as an example). I have 
> started adding some K2SO4 to my tanks partly because of this discussion 
> and partly because I think that I have a K deficiency.
>
	I know it isn't proof, and I agree wholeheartedly about the 
quality of aquarium information, which is why Kevin and I presented
this as an hypothesis.  Would you please take measurements of the nitrate
concentrations in your tank now you are adding potassium?  I would like to
hear the results - I would predict a drop if trace elements are there.
 
> I hope that the authors do not take this as personal criticism, it is 
> not. I know how difficult it is to design experiments to prove something. 
> Their evidence also fits with general information here in australia. Our 
> soils are generally deficient in P and so that is the fertiliser that is 
> used and it is runoff from those fields that causes our algal blooms.
>
	I don't take it as personal criticism.  We posted this information 
because we thought it would be of interest, and to encourage experiment
and reporting of results.

	In retrospect, I wish I had written down, in detail, what I was
doing with my tank, and the observations I made.  I'm sure I lost a lot
because memory sometimes fails.  I would encourage others to keep a log,
preferably daily, and at any rate weekly, for each tank.

	Thanks for your interest.


Paul Sears     Ottawa, Canada



------------------------------

From: Paul Bucciaglia paul-b-at-biosci.cbs.umn.edu
Date: Wed, 3 Apr 1996 08:03:55 -0600 (CST)
Subject: Re: Sears and Conlin paper
Comment 1 Comment 2 

Interesting paper, guys.  I have a couple quesitions.

First, do you have the  final concentrations (in aquarium) of the 
nutrients in PMDD.  We need to start talking about final concentrations, 
and not just relative levels or concetrations in a fertilizer mix.  Its 
calculatable from the info in your paper, just wondering if you have it 
handy.

Second, do you have any ideas on why many people (ie Dupla users) can get 
good results without additional N (other than fish food).  I think would 
be an interesting topic for the Discussion.

Thanks for posting your article,

paul Bucciaglia
 

------------------------------

From: Kevin Conlin kcconlin-at-cae.ca
Date: Wed, 03 Apr 1996 11:50:42 -0500
Subject: Re: Algal control in the aquarium

On Wednesday, 3 April 1996, Peter Hughes wrote:

> In the abstract it is mentioned that the micronutrients, N and K should 
> be in slight excess of P to provide algal control. I can see that this 
> may be true, but it should only be true if P then becomes limiting. If 
> the general feeding strategy/fertiliser reserves are high in P then it 
> will still remain in sufficient excess to cause problems.

Very true.  For large values of P, the lighting could become the
limiting factor.  For even larger values, an aquarium packed to the
gills with plants growing at their maximum rate would not be P
limited.  Fortunately, this situation is unlikely to occur in an
aquarium unless uncomposted manure is used as the substrate.

> 1. the tanks are individual tanks and have not been duplicated in any 
> way.

We're working on this.  A number of individuals are now attempting to
reproduce our results.

> This may be seems a bit strange, but it is impossible to know if the 
> tanks would have gotten over those same algal problems by themselves. 
> This sort of experiment can probably only be carried out in a tank that 
> is divided after an initial period of running in, with the same planting 
> on each side. This is difficult to do but would give some valuable data in 
> terms of the difference in plant growth and what the algal population 
> differences are.

We've been careful to point out that our experiments were uncontrolled.

> 2. Repeated addition of P to the, supposedly, P limited tanks and careful 
> observation of algal populations. Only by adding pure P over several 
> succesive cycles will show the dependency of algae on P. The fertiliser 
> tablets that remain undissolved in the substrate in case 2 may be 
> providing some other nutrient that sets off the algal bloom and not 
> necessarily P. The single addition of Phosphate and the resulting 
> observations do give a pretty clear indication about what is going on, 
> however it needs to be taken a bit further than it already has been.

I may repeat the the phosphate experiment, but it's such a shame
to create an algae bloom in a nearly algae-free tank...

> So what do I think of this evidence, I think that it is very interesting, 
> but stops just short of being proof.

We're not offering proof.  We're offering a hypothesis that fits our
observations.  It's a very testable hypothesis, and we hope others
will be inspired to continue the work.

> In saying this I am being a bit of a 
> devils advocate, but so much aquarium information is not really good 
> enough to be called fact (see recent discussions on the 
> useability/unavailability of ironIII in aquaria as an example).

Very little of the information out there is good enough to be called
fact.  The paper is partly in response to the lack of good information;
we're trying to get people pointed in the right direction.  Endless
debates don't prove anything; careful experiments and observations do.

> I hope that the authors do not take this as personal criticism, it is 
> not.

Criticism (preferably constructive) is an important part of the excercise.
Without it there can be no progress.
- --
Kevin Conlin   kcconlin-at-cae.ca   "We're Canadians.  We HAVE to be polite"
Finger as332-at-freenet.carleton.ca for PGP public key.


------------------------------

From:  David Whittaker ac554-at-freenet.carleton.ca
Date: Thu, 4 Apr 1996 06:24:14 -0500
Subject: PMDD Paper
Comment 1  Comment 2  Comment 3

      COMMENTS ON "Control of Algae in Planted Aquaria

The initial conditions of Case #1 include a UV sterilizer. That
couldn't have helped your dissolved iron levels. In Case #2 you
installed a carbon filter to the same effect.

"Because others have observed that tanks with CO2 fertilization have
relatively little red algae [5], it tempting to speculate that at
least some red algaes are able to utilize bicarbonate, giving them an
advantage in aquaria where most of the available carbon is in this
form (typically those with high carbonate hardness and high pH)."

"Red algae is favored over green algae if most of the available
carbon is in the form of bicarbonates."

While the red beard/brush algaes seem to take off when my DIY CO2 
runs out, that may simply be due to diminished competition with the
plants. I wouldn't be tempted to conclude the above until I had
better proof. It is a pretty broad generalization and there sure
are a myriad of red algaes. 

Why do you advocate 0.1 ppm iron as opposed to 0.3 ppm?

If you check The Optimum Aquarium page 70, you will notice that of
the cations present in the water, only potassium and sodium are
available in proportionately large amounts. On page 68 mains water
is compared to water in the cryptocorne areas. Note the abundance
of sodium and potassium in the latter. This tells me that, within
reason, one should not be afraid of overdosing with potassium and
that one would be better off substituting KCl for K2SO4 in the PMDD.

I had a similar experience to Case #1 when my experimental 29 gallon
was just set up with the Webb-Kelly RUGF. I had put a pond tab bits
in the substrate and within a few days green-spot algae appeared. It
also seems to favour bright light (I had installed a new MH bulb).
It was eventually replaced by beard algae. Every algae has its
day.

I was a fool for assuming over the years that the 0.8 ppm potassium
and the 2.3 ppm magnesium in the water supply would surely be
adequate. Although I had warned others in an AGA article in 1992
to watch out for potassium deficiency, I have not followed my own
advice until very recently. Reviewing some old hydroponic data that
I'd copied as well as George Booth's recent post of Dupla information,
it appears that quite a lot of potassium is required by aquatic
plants, more than almost any other nutrient, and in greater quantities
than required by terrestrials.

Your hypothesis rings true. I'll suggest two possible reasons for
this. In the wild many of our ornamental aquatic plants grow in
waters of very low nutrient levels. Perhaps, in the case of the
algae, a higher threshhold of phosphorus must be attained before
intake occurs. Growth then takes off. Macrophytes are more adaptable,
complex, the processing takes longer and there may be more inter-
mediate steps, i.e. long term storage, conversion, and retrieval.
If phosphorus levels in the water are very low the ability to store
this element becomes critical. It might explain why my system of ad
hoc additions of hydroponic nutrients every few days has produced
mostly algae. This is what my neighbour has been saying for years.
He has two immaculate planted no-tec tanks. He uses Micronutrient
Mix, no CO2, good filtration and a double fluorescent fixture.
Growth of course is slow but steady. I recently gave him some
K2SO4 since some of his swords appear to be potassium deficient.

The above question must have been addressed many times in the
specialist literature. This is how governments prefer to spend
their research dollars.

MY EXPERIENCE WITH PMDD:

About ten days ago I mixed up a batch of PMDD for daily dosing. Three
of four tanks are better, two most noticeably. As you have said it's
the stability of the levels and of the proportions of the nutrients
that is also important. Daily dosing ensures that the plants are always
growing at least marginally and able to use the phosphorus constantly
released by the substrate, by the fish, or by plant decay.

Since switching to PMDD the experimental tank has undergone drastic
change. Previously most of the plants were wearing coats of short,
black, brush algae. The SAEs hadn't a hope in hell of keeping up. I
removed the five ottocinclus and the three SAEs. Seven days later it 
is dying back and being replaced by mostly filamentatious green stuff.
The plants are growing slowly and are probably phosphate-limited. There
are no fish in the tank and lots of light. Next week I plan to add
fifteen white clouds to see what effect their metabolic activity
generates.

The best tank is a fifteen gallon with 8 otocinclus and three spawning
rasbora maculata. One week after starting the daily PMDD regimen, all
the plants are doing fine, oxygen bubbles are visible, and there is
only a bit of green spot algae on the lilaeopsis. It is the only tank
which was bleach-treated several months ago. One food tablet and 1 ml
of PMDD enters the aquarium daily.

The third tank, the 180 gallon, is now always well-oxygenated which
had been the case only sporatically before using PMDD. It is lit by
only four 40 watt fluorescent lamps and supplied with DIY CO2. It's
still covered in black brush algae.

The algae in the fourth tank apprears to have stopped growing, but
no retreat is evident yet. The water sprite is growing at a phenomenal
rate and obviously sucking up nutrients.

With respect to blue-green algae I concur with you two. It appears
after the plants stop growing. This has occurred when my CO2 ran out,
when there were no fish to supply nutrients, and when the water was
left for weeks without fish or a water change. The common thread is
water depleted of nutrients. The algae starts to take off as the
plants decay and die back. Interestingly, a small tank that contains
just java moss, no filtration, little light, and gets a pinch of
fishfood has never had blue-green algae. The java moss is always
growing.

All in all I think that you guys are dead on. Heartening is your
discovery that algae can be eliminated without predators. Before now
I never believed that phosphate levels were necessarily the culprit.

By the way, I've come to the conclusion that the vermiculite/clay 
substrate and my Webb-Kelly system was a nice try but doesn't win
a ribbon. Some of the crypts like to root in the sandy clay. I
suppose one could discontinue the reverse flow and simply pour
nutrients down the tube and into the plenum, hoping for a very slow
diffusion and playing the guessing game again. This might work well
with non-chelated micronutrients, phosphorus and ammonia on a daily
basis, while adding magnesium and potassium to the water column. It
avoids the mess of cow manure. The vermiculite would act as a buffer
for the cations and the ammonia.

Ten days isn't long. The PMDD technique works better than what I
had been doing. Three months will tell. I'm going to have to invest
in nitrate and phosphate test kits. Any recommendations?



- --
Dave Whittaker                       ac554-at-FreeNet.Carleton.CA
Gloucester, Ontario                  dwhitt-at-magmacom.com
Canada

------------------------------


From:  Paul Sears psears-at-NRCan.gc.ca
Date: Thu, 4 Apr 1996 11:30:11 -0500 (EST)
Subject: Re: Algae, phosphates

> From: nfrank-at-nando.net (Neil Frank)
> 
> Regarding the effect of P, there was an interesting article published in TAG
> which is an English translation of one originally published in AquaPlanta
> (see TAG, V7n1). The author, Peter Peterson, slowly reduced phospahte
> concentration by adding a 0.3% solution of of iron chloride (over 8 day
> period). He reduced the Phosphate concentration to 0.1 ppm. During this
> time, he observed that some species of higher plants started to suffer and
> algae bloomed. This suggests that his algae was able to utilize phosphates
> at a lower level than some of his plants. He observes that the results may
> be species specific.
>
	Do you have the original reference?  I would be very interested to 
see it.  Adding FeCl3 to take out phosphate would probably take out most
of the trace elements as well, unfortunately.  They would be very prone
to adsorption on the colloidal iron hydroxide/oxide that took the 
phosphate down.
 
> With extra feeding he brought the conc back to 0.6 and deficiences vanished.
> He concludes that a range of P concentrations may be optimal for good plant
> growth without algae. He thinks that 0.2 ppm is too low. The article had
> many other interesting obsevations about levels and different types of
> aquarium plants and growing conditions. The above also supports Peter who
> said "Only by adding pure P over several succesive cycles will show the
> dependency of algae on P"
> 
	Again, the "extra feeding" would provide a lot more than phosphate.
As pointed out earlier, we need experiments with only one variable!
The interesting point is the apparently satisfactory functioning of the
aquarium at phosphate levels that were very high according to some
earlier postings.  I seem to recall 50 ppb being mentioned as lots.
Kevin and I never claimed that limiting phosphate is the only way to
good results, just that we think that that is how our tanks are functioning!

Paul Sears    Ottawa, Canada

------------------------------

From: Kevin Conlin kcconlin-at-cae.ca
Date: Thu, 04 Apr 1996 11:47:47 -0500
Subject: Re: Sears and Conlin paper
Comment 1

On Wednesday, 3 April 1996, Aquatic-Plants-Owner-at-ActWin.com wrote:

> First, do you have the  final concentrations (in aquarium) of the 
> nutrients in PMDD.  We need to start talking about final concentrations, 
> and not just relative levels or concetrations in a fertilizer mix.  Its 
> calculatable from the info in your paper, just wondering if you have it 
> handy.

If you dose for the recommended 0.1ppm Fe, you'll get about 0.5ppm Mg,
0.02ppm B, 0.03ppm Mn, 0.001ppm Mo, 0.006ppm Zn, and 0.001ppm Cu.
K and N depend on tuning; the base PMDD provides 1.3ppm K and 0.6ppm NO3.
Since only Fe is being measured, there's no way of knowing exactly how
much of the other trace elements are in solution.  Additional trace
elements come from the fish food.  We don't think absolute concentrations
are as important as simply having more than enough for the amount of
phosphate available.  Excess elements are removed through regular water
changes.

> Second, do you have any ideas on why many people (ie Dupla users) can get 
> good results without additional N (other than fish food).  I think would 
> be an interesting topic for the Discussion.

This issue is complicated by substrate additives such as laterite.  There
is no way of knowing (for me, anyway) what these additives contribute other
than iron.  In a tank with a relatively inert substrate, using the Dupla
water conditioners, tablets, and drops, I would expect that tanks with
a low fish load would do relatively poorly due to trace element and
macronutrient deficiency.  With a moderate to high fish load, the fish
food would provide the trace elements and macronutrients, and the plants
would do fine.  However, the food would provide excess phosphate, so the
algae would also prosper. I predict, with tongue firmly in cheek, that there
is a high probability of finding SAEs in Dupla tanks.
- --
Kevin Conlin   kcconlin-at-cae.ca   "We're Canadians.  We HAVE to be polite"
Finger as332-at-freenet.carleton.ca for PGP public key.

------------------------------
From: Kevin Conlin kcconlin-at-cae.ca
Date: Thu, 04 Apr 1996 17:42:05 -0500
Subject: Re: PMDD Paper
Comment 1

On Thursday, 4 April 1996, David Whittaker wrote:

> The initial conditions of Case #1 include a UV sterilizer. That
> couldn't have helped your dissolved iron levels. In Case #2 you
> installed a carbon filter to the same effect.

I looked into the effect of the sterilizer on my iron levels ages ago.
You may recall the discussion on the subject here in the APD.
After much mucking about, I concluded that the sterilizer wasn't
having much effect at all; turning the sterilizer off didn't make any
discernable difference to the iron readings.  There may indeed be some
effect, but my iron test kit isn't sensitive enough to detect it.

> While the red beard/brush algaes seem to take off when my DIY CO2 
> runs out, that may simply be due to diminished competition with the
> plants. I wouldn't be tempted to conclude the above until I had
> better proof. It is a pretty broad generalization and there sure
> are a myriad of red algaes. 

Blatant speculation on my part (and clearly labeled as such).
Baensch and others note that red algae seems to disappear with
CO2 fertilization.  I was hoping that someone would come forward
with data from real studies.  Somewhere there is someone studying
freshwater red algaes for his PhD; would this person please step
forward?  We won't make fun of you, really we won't.

> Why do you advocate 0.1 ppm iron as opposed to 0.3 ppm?

It seems to be enough.  My Sera test kit has its first color sample
at 0.25ppm, so I'm only guessing at my actual level.  I barely show
any iron at all.  I think Paul uses the same kit.  Within reasonable
limits, a little excess iron or other trace element probably won't
hurt anything, provided regular water changes are done to prevent
accumulation.

> This tells me that, within
> reason, one should not be afraid of overdosing with potassium and
> that one would be better off substituting KCl for K2SO4 in the PMDD.

We picked K2SO4 because it's also a source of S, and because we weren't
keen on having too many Cl- ions floating around.  At the concentrations
we're talking about, chloride isn't likely to be a problem, but we aren't
using KCl in our own tanks and therefore we can't recommend it.

> The above question must have been addressed many times in the
> specialist literature. This is how governments prefer to spend
> their research dollars.

I keep hoping to dig up some of this literature.  Can anyone help?
The relationship between phosphorus and algae has been known for a
long time (hence phosphate-free detergents); there must be a ton
of literature out there.
- --
Kevin Conlin   kcconlin-at-cae.ca   "We're Canadians.  We HAVE to be polite"
Finger as332-at-freenet.carleton.ca for PGP public key.

------------------------------

From: Karen A Randall krandall-at-world.std.com
Date: Fri, 5 Apr 1996 13:39:27 -0500
Subject: Algae control, RO water use

Subject: Re: Sears and Conlin paper

> > Second, do you have any ideas on why many people (ie Dupla use
> > good results without additional N (other than fish food).  I t
> > be an interesting topic for the Discussion.
> 
> This issue is complicated by substrate additives such as laterit
> is no way of knowing (for me, anyway) what these additives contr
> than iron.  In a tank with a relatively inert substrate, using t
> water conditioners, tablets, and drops, I would expect that tank
> a low fish load would do relatively poorly due to trace element 
> macronutrient deficiency.  With a moderate to high fish load, th
> food would provide the trace elements and macronutrients, and th
> would do fine.  However, the food would provide excess phosphate
> algae would also prosper. I predict, with tongue firmly in cheek
> is a high probability of finding SAEs in Dupla tanks.

I know that you are poking fun, but I'd like to point out that in 
my tanks, which do NOT have a high fish load, and are not heavily 
fed, and supplemented with Dupla drops and tablets I have not seen 
much sign of macronutrient deficiency.  I have always had very 
good growth.  

I also have not had any real algae problems that were not 
attributable to an isolated event. (like the time I inadvertently 
ran out of CO2, and could not get the system back on line for over 
a week)  Until about 6-9 months ago, SAE's were not available in 
this area, so it the lack of algae was not attributable to their 
presence.  In fact, the only algae eating fish were a group of 
Otos in each tank.  While I like Otos a lot, I don't think they 
are big enough to make a dent in "problem" levels of algae.

I like keeping SAE's now that they are available, because I don't 
have to worry about them starving if algae levels are low, which 
is always a worry with Otos.

- ------------------------------

From:  Paul Sears psears-at-NRCan.gc.ca
Date: Fri, 5 Apr 1996 19:12:18 -0500 (EST)
Subject: UV sterilizers, Mg chelation, etc.
Comment 1

> From: ac554-at-freenet.carleton.ca (David Whittaker)
> 
> The initial conditions of Case #1 include a UV sterilizer. That
> couldn't have helped your dissolved iron levels. In Case #2 you
> installed a carbon filter to the same effect.
>
	Why would you expect the UV sterilizer to affect the iron
concentrations?  I can't see any reason to expect that.  In case
2 the carbon filter was removed when the trace element addition
started.
 
> one should not be afraid of overdosing with potassium and
> that one would be better off substituting KCl for K2SO4 in the PMDD.
> 
	Why would you prefer Cl- to SO4-- in the tank?  The plants
can use sulphur in fair quantities, and I don't think they need
all that much chlorine.

> 
> Ten days isn't long. The PMDD technique works better than what I
> had been doing. Three months will tell. I'm going to have to invest
> in nitrate and phosphate test kits. Any recommendations?
>
	I'm using a Wardley dry tablet test kit for nitrate, and it
seems to work well.  I ran checks on deionized water and on a test
solution of 40 ppm nitrate, and they gave good results.  I have (so
far) refused to pay $20+ for 20 phosphate tests.  I have been looking
in analytical textbooks to find a method that will function at a low
enough level.  If "Dr. Dave's" remark in Febrary that 0 - 30 ppb is
about right, then I doubt that I shall find anything suitable.
 
> 
> Depends upon your chloramine levels which could be 0.5 ppm to 2.0 ppm
> or above. If you use four times the recommended dosage for chlorine
> written on the bottle, you are almost guaranteed to be alright. I have
> no idea how or if it affects micronutrients.
> 
> and
> 
> Paul Sears wrote...
> >Hopefully Dave W, will fill us in....
> 
> I'm not going to get sucked into this with my very limited knowledge
> of chemistry. I'll send you the article I mentioned by a Gary Zimmerman,
> Department of Physiology, University of California. You can figure it
> out for us.
>
	I now have it.  Thanks.  Thiosulphate should work for chloramine
in much the same way as it does for chlorine.  A somewhat higher dosage
may be required for the same number of ppm chloramine as chlorine, 
because the former has a lower molecular weight (51.5 vs 71, so use
about 1/3 more).

> I have one question about PMDD. Will the magnesium have a tendency to
> replace the chelated micronutrients in the concentrate? Maybe it is
> better to keep it out of the mix and add it separately.
> 
	Good question, and one I should have investigated more already.
I'll see what I can find out about the relative stabilities of the
chelates. 


Paul Sears   Ottawa, Canada

------------------------------

From: Neil Frank nfrank-at-nando.net
Date: Fri, 5 Apr 96 19:53:44 EST
Subject: KCl vs K2SO4
Comment 1 

From Paul S.
...
      >>  Why would you prefer Cl- to SO4-- in the tank?  The plants
can use sulphur in fair quantities, and I don't think they need
all that much chlorine.<<

I use KCl because I have a life time supply (from hardware store - muriate
of potash). I don't have a conventient supply of the other, but could get it
from a chemical supply house if necessary. I never thought it was important.
Although I agree that the S is more useful than Cl, my tap water already has
25ppm S. And I had been adding Epsom salts for the Mg and some extra S.

Do you think that continuing to adding a ppm or so of Cl together with
weekly or biweekly 25 % water changes could be bad? Assuming no Cloride
assimilation, what would be the concentration at the end of a few years? 

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


------------------------------

From:  Paul Sears psears-at-NRCan.gc.ca
Date: Sat, 6 Apr 1996 19:19:52 -0500 (EST)
Subject: Re: chloride vs. sulphate

> From: nfrank-at-nando.net (Neil Frank)
> 
> Do you think that continuing to adding a ppm or so of Cl together with
> weekly or biweekly 25 % water changes could be bad? Assuming no Cloride
> assimilation, what would be the concentration at the end of a few years? 
>
	At that rate, assuming you meant a ppm or so of Cl- based on the
contents of the whole tank, you should stabilize at about 4 ppm very
quickly, which I doubt would cause problems.

Paul Sears   Ottawa, Canada 


------------------------------

From:  Paul Sears psears-at-NRCan.gc.ca
Date: Sat, 6 Apr 1996 19:35:53 -0500 (EST)
Subject: Re: Iron EDTA complex
Comment 1  Comment 2

> From: ac554-at-freenet.carleton.ca (David Whittaker)
> 
> Paul Sears writes...
> >Dave Whittaker wrote...
> >	Why would you expect the UV sterilizer to affect the iron
> >concentrations?  I can't see any reason to expect that.  
> 
> I believe that someone, maybe GB, found that UV use caused his
> iron levels to fall. This makes sense in that it is known that
> light speeds up the breakdown of FeEDTA in solution.
>
	Do you have a reference for that?
  
> 
> From: Elizabeth Worobel <eworobe-at-cc.UManitoba.CA>
> 
> The formation constant for FeEDTA is 25.1 (log Kmy). The formation 
> constant for Mg is 8.7, for Ca 10.7, for Cu 18.8, and for Zn 16.5 (under 
> standard conditions). As these are log values it is clear that EDTA binds 
> iron MUCH more tightly than any other cation ... I dont think you have to 
> worry about Fe being displaced. Info from Skoog and West, Fundamentals of 
> Analytical Chemistry, 2nd Ed, 1969, p. 345.
> 
> Dr. dave.
>
	Thanks.  At that rate there certainly isn't a problem!

Paul Sears   Ottawa, Canada

------------------------------

From: Elizabeth Worobel eworobe-at-cc.UManitoba.CA
Date: Sun, 7 Apr 1996 11:25:02 -0500 (CDT)
Subject: Re: EDTA photodegradation
Comment 1

Frank, R. and Rau, H. 1990. Photochemical transformation...of ... EDTA. 
Ecotoxicology and Environmental Safety 19: 55 to 63.

Lockhart, H. B. and Blakely, R.v. 1975. Aerobic photodegradation of ... 
Ferric EDTA. Environmental Science and Technology 12: 1035 to 1038.

------------------------------
From: Franc Gorenc franc-at-golden.golden.net
Date: Tue, 9 Apr 1996 00:57:29 +0000
Subject: Re: Diethylene triamine pentaacetic acid

On  Sun, 7 Apr 1996 19:35:28 -0500
Paul Krombholtz wrote....

> Subject: Re: EDTA photodegredation
> 
> When I was growing aquatic plants in algae-free culture back around
> 1966-68, I noticed that I had a precipitate in flasks of nutrient solution
> plus iron EDTA that had been exposed to light, but no precipitate in
> identical flasks kept in the dark.  However, enough iron stayed in solution
> to grow the plants satisfactorily.
> 
> Currently, I am using iron DPTA, (diethylenetriaminepentaacetic acid),
> which appears to stay in solution a lot longer.  CIBA-Geigy, agricultural
> chemicals division,  makes it, but it is hard to find in your average
> garden store.
>

Yes. There are three chelates commonly used to sequester trace metals.These 
are: EDTA        ethyline diaminetetra acetic acid
       DTPA        diethylene triamine pentaacetic acid
       EDDHA     ethilene-diamine dihydroxyphenyl acetic acid
EDDHA  and DTPA chelate iron only. EDTA associates with copper, zinc, 
manganese, bivalent iron(Fe++), and trivalent iron(Fe+++). All three chelates 
are less stable at higher pH than lower pH. The stabilities of all three are 
also adversly affected by light.
FeEDDHA is by far the most stable at higher alkalinities and it is the 
preferred form where there is a  high concentration of  calcium bicarbonate.
FeEDDHA is expensive and  often difficult to obtain. It is very efficient and 
only a fraction is needed to do the job as compared with FeEDTA. The company 
that sells it is CIBA-GEIGY Corp, Box 11422, Greensboro, NC 27409. But they 
won't sell you just a spoonful. :-).
FeEDTA is at least stable. At pH above 7.0  80% will decompose after two weeks.
It is used commonly because it is cheap and because it is a good product to 
chelate all four trace metals.
To maintain greater iron solubility FeDTPA is often added to FeEDTA. The former
is slightly more stable than the latter. When added together a boosting effect 
occurs and the mixture is as stable as FeDTPA alone.
By the way Paul where did you get it ??

Further reading... P. Fisher   Stability of various forms of chelated iron in 
nutrient solutions of different pH values, ISOSC Proceedings 6th International 
Congress on Soilless Culture  1984, pp. 225-233

Franc Gorenc                           franc-at-golden.net
Kitchener, Ontario                  http://www.golden.net/~franc
Canada

------------------------------
Later comments and related information.
Up to Fertilizer <- Plants <- The Krib
This page was last updated 29 October 1998