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



  1. Shelf life of Flourish/Substrate iron
    by Beverly Erlebacher <bae/> (Fri, 13 Nov 1998)
  2. Seachem Flourish Question
    by Greg Morin <greg/> (Tue, 22 Dec 1998)
  3. Research topic
    by Greg Morin <greg/> (Mon, 15 Mar 1999)
  4. Seachem Flourish
    by Michael <wantbeer/> (Mon, 06 Sep 1999)
  5. Seachem Excel
    by Roger Miller <rgrmill/> (Thu, 3 Jan 2002)

Shelf life of Flourish/Substrate iron

by Beverly Erlebacher <bae/>
Date: Fri, 13 Nov 1998

> From: "Christopher Coleman" <>
> Steve, I have recently spoke with Sechem regards the Flourite soil substrate
> product which is a calcined clay product.  It has iron ... ferric iron. 

As far as I can tell, Flourite is a low-temperature fired iron containing
clay, basically kiln-fired kitty litter.  It would be about as soluble as
crushed terra cotta flower pot.  Not to say that this is negligible -
try soaking a terra cotta flowerpot in a bucket of water with muriatic
acid and you may be surprised at how red the water gets.

> They also
> mentioned their Flourish and Flourish Iron fertilizers contain non-chelated
> iron ... ferrous gluconate.  Subsequent to the conversation I posted the
> message
> below which I had hoped could be answered by some of the chemists on the
> list as I felt the interest in Iron and Iron test kits is always popular
> here as indicated also by the current thread.

I'm not much of a chemist any more, but since nobody else has commented,
I'll have a go at it.

Btw, it is mildly amusing to find out that Flourish is ferrous gluconate.
I sometimes take an iron supplement to prevent anemia, and I buy a local
'house brand' of ferrous gluconate or fumarate about $5Cdn (~$3+US) for
100 tablets containing 300mg Fe gluconate each.  300mg of Fe gluconate
contains 34.7mg of elemental iron, according to the bottle.  This may be of
interest to anyone who wants to make their own Flourish-equivalent and has
access to a drugstore.  Personally, I bought 250g of Fe-DTPA for $3 some
years ago, and I expect it to last me far into the new millenium.

> I have just got off the phone with Seachem technical support and been
> informed that the Iron supplied in their Flourish line of products is non-
> chelated, that it is ferrous  gluconate, and that this makes it better than
> many other iron supplements which are chelated.

I wouldn't be surprised to learn that gluconate has a mild chelating or
reducing action that helps preserve the iron in the ferrous state, but 
in that case I'd expect Seachem to brag about it.

> I was then reminded of the many posts on the APD which indicate that
> neither the Lamotte or Hatch test kits test for chelated iron. Yet most of
> us get measurable numbers from these test kits.
> Could one of more chemically inclined APDers remove some of the
> confusion surrounding the statements the test kit manufacturers are
> making versus the results which we obtain in practice?  I have read that
> it is possible the test kits can still be accurate, that the measurements
> we get are as a result of the iron comming unchelated.
> But if the iron did become unchelated, it raises the question, how fast and
> how completly was it unchelated by the time we test it? (did it measure all
> the iron)

Ok, here's my take on this.  Btw, I have never used a test kit for iron.
If my plants don't look green enough for my taste, I sometimes add a tiny
pinch of Fe-DTPA to the tank.  This happens once or twice a year, but my
tap water has a bit of iron in it.

Chelation is an equilibrium process with a strong tendency to the chelated
form.  So a solution of chelated iron will have a very small amount of the
iron in the free form, since it is constantly dissociating and recombining.
Some people find that when they use iron test kits, they get a low reading
right away, but if they leave it a few hours, the solution gives a much
higher reading.  My guess is that the test reagent is grabbing the iron ions
whenever they are released by the chelator, so the immediate reading reflects
the level of dissociated iron at equilibrium, but as time passes and the 
reagents grab more and more of the iron before it can recombine with the
chelator, the reading reflects total iron.  Presumably the plants take up
ferrous ion from the constantly available minute amounts that are not 
chelated, although I think I've read that land plants, at least, may secrete
chelators from their roots and reabsorb the chelated minerals as such.

> Additional questions regards iron I have:
>   1)  in measurements I have made using Dupla drops in a
>        bucket of tap water, the iron levels remain stable
>        over the period of a period of a week.  This seems to
>        contradict what I have read that iron is unstable. Any
>        insight?

The chelating agent protects the ferrous ion from being oxidized to ferric
ion.  It's this oxidation that is referred to when ferrous ion is described
as being unstable in water.

> 2)   Does anyone know if the Dupla products are
>        chelated and by which chelate?

I would guess yes, and probably EDTA, maybe DTPA.

> 3)   Is there really any benefit to non-chelated iron
>        versus chelated ferrous iron?

Plants use ferrous iron.

I hope this helps.  Real chemists, please feel free to correct the above


End of Aquatic Plants Digest V3 #643

To unsubscribe to aquatic-plants, send the command:
    unsubscribe aquatic-plants
in the body of a message to "".  Archives are
available on the web at
or via FTP to in /pub/aquaria/aquatic-plants.

Seachem Flourish Question

by Greg Morin <greg/>
Date: Tue, 22 Dec 1998

> This is primarily directed to Greg Morin, but I thought others might be
> interested in the answer. A friend of mine, who happens to own a 
> lfs, recently
> received a shipment of Seachem products. He called a Seachem 
> employee, identified
> only as Collin, to inquire about the ingredients in Flourish. Upon 
> hearing that
> Flourish contained little or no Nitrogen, Phosphorus, or Potassium, 
> he inquired
> where the plants were going to obtain these major nutrients. Specifically, I
> believe he was mostly interested in Nitrogen, since he was/is 
> having a mild cyano
> problem in his display tank, and I had mentioned that I thought 
> that it might be
> N limited. (tests later proved N levels to be very low) Collin 
> replied that he
> considered ideal nitrogen levels to be zero.
> My questions are:
>  1. Does Seachem believe that ideal N levels in a planted aquarium should be
> zero?
>  2. If not, where does Seachem expect N-P-K to be supplied from 
> since there is
> very little contained in either
>      Flourish or Flourish Tabs?

Let me first say that Colin is currently in training and while that 
is not an excuse I think this is why he missed a subtle distinction 
here that resulted in him giving correct albeit incomplete and a 
little misleading information. The distinction I'm referring to is 
between nitrate vs nitrogen and phosphate vs phosphorous. Flourish 
does not contain nitrate or phosphate per se, but it does supply a 
nitrogen source, the Nitrogen equivalent being 400 ppm in the bottle. 
Phosphorous is not available as free phosphate but as phosphate 
esters (100 ppm). Flourish does in fact contain potassium (600 ppm) 
but like with the iron, you wouldn't want to use Flourish as the sole 
source of potassium maintenance if the potassium is heavily utilized. 
While I can't comment on unannounced products, I can say that you can 
expect to see some products in the near future that will complement 
the current products and give the hobbyist more control over specific 
water parameters.

Now to directly answer your questions ;-)

1) I suspect Colin either said or meant "nitrate" and not "nitrogen" 
should be zero... although that is still a bit of an 
oversimplification. Obviously the plants need a source of nitrogen. 
Plants utilize ammonia preferentially over other sources of nitrogen. 
So optimally you would want your main source of nitrogen to be 
ammonia (from fish) and you would want this source utilized 
completely. In this case there would be no excess ammonia and thus a 
zero level of nitrate (because there is no excess ammonia to be 
converted to nitrite->nitrate). Thus an ideal set up would be one 
where the ammonia reading was 0 and the nitrate reading was 0. 
However, in practice this can be a "flying blind" approach because 
you will still have 0 readings if you don't have enough ammonia to 
satisfy the needs of the plants. So in practice you really do want to 
have a slight nitrate reading (under 10 mg/L should be perfectly safe 
for a planted tank). The excess tells you that the plants are getting 
all that they need and still have a slight amount left over.

2) Seachem supplies an NPK source in its Flourish, however the levels 
we set in the product are meant to complement the other natural 
sources (here I'm referring to P & N) of these elements. If you have 
even a few fish in your planted tank they should provide sufficient 
levels of nitrogen and phosphorous. One advantage with Flourish is 
that the nitrogen source is in the form of amino acids which are 
utilized as preferentially as ammonia is and even if the amino acids 
are broken down by bacteria, it is broken down in to ammonia first 
which can be utilized by the plants as well.  The amount of these 
constituents that we put in Flourish is enough to be of a benefit but 
not so much that if you have a number of fish you are not going to be 
adding an excess of N & P if you are using Flourish. If you have no 
fish at all and no other non plant species, then the amount of N & P 
in Flourish is probably not going to be sufficient (of course 
depending on the number and size of your plants)... in this case a 
good economical approach would be to either get a couple of 
inexpensive fish or add a bit of an ammonia solution (IMHO).

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

- -Greg Morin

P.S. Thank you for bringing this call to our attention... we will be 
clarifying this with Colin.

Gregory Morin, Ph.D.  ~~~~~~~Research Director~~~~~~~~~~~~~~
Seachem Laboratories, Inc.     888-SEACHEM

Research topic

by Greg Morin <greg/>
Date: Mon, 15 Mar 1999

> Also, the fertilizer 'Flourish' claims to be a balanced fertilizer that
> "... contains no phosphates or nitrates that would promote algae
> proliferation."  It is very important that we keep the phosphate level
> at 0 in the other tank, does anyone know if there is no phosphate
> whatsoever in this fertilizer?

It does not contain any free phosphate (PO4 3-). The guaranteed 
analysis lists less than 0.01% Phosphorous which comes from small 
amounts of phosphate _esters_, not free phosphate. Anionic phosphate 
esters are very hydrolytically stable (i.e. very slowly hydrolyzed by 
water to free phosphate)...  (incidentally, this is why DNA is so 
stable). Because of this stability very little of that already small 
<0.01% will ever hydrolyze to free phosphate.

- -Greg Morin

Gregory Morin, Ph.D.  ~~~~~~~Research Director~~~~~~~~~~~~~~
Seachem Laboratories, Inc.     888-SEACHEM

Seachem Flourish

by Michael <wantbeer/>
Date: Mon, 06 Sep 1999

> Can anyone on this list explain to me what exactly Seachem Flourish is?

You can get a detailed analysis of what is in Flourish at Seachems
website, heres a direct link:

> I bought some through a mailorder company under the category of plant
> fertilizer and it arrived with nothing except a scant label that said it is
> a "non-fertilizer water conditioner'
>What exactly does it contain and what does it do?

As to why it is referred to as a "water conditioner"...  The following
is ripped directly from there FAQ at:

"Q: Why did you change the product? 
A: We didn’t change the product at all, only the label. This was a
result of ill defined state fertilizer laws which make it impossible for
us to sell the product with the older, more descriptive label. These
laws do not consider aquaculture fertilization parameters and therefore
left us with the choice of either bottling 10/10/10 or changing our
labels such that no fertilization claims were made. These laws have been
recently changed at the federal level, so hopefully in the not too
distant future, the consumer will not have to guess at what certain
products do because of overly restrictive government regulation." 

Also ripped from their site is what they say it will do: 

"Flourish™ is a growth stimulator for aquarium plant stems and leaves.
It contains a broad spectrum of essential trace elements, vitamins, and
amino acids. Flourish™ is rich in gluconate iron, manganese, calcium,
magnesium, potassium, inositol, choline B12, biotin, and other factors
that have been determined to be beneficial to aquatic plants. It
contains no phosphate or nitrate or other fertilizers that would promote
algae proliferation. A 100 mL bottle treats up to 5,000 gallons. It is
also beneficial for household plants."

I use it without the Flourite, Flourish Tabs, or Flourish Iron.
You can also find info on their other products at their site.

Hope this helps,

Seachem Excel

by Roger Miller <rgrmill/>
Date: Thu, 3 Jan 2002

On Thu, 3 Jan 2002, Daphne wrote:
> I have been happy with the Seachem line (as well as their phenomenal
> customer service) so I decided to give it one more try (at a much lower
> dosage).  Algae does seem to be going away.  I am still manually removing
> some but not as much and not as often.  My new A. ulvaceous has doubled in
> size and my Christmas moss is going nuts.  Haven't seen any major
> differences in anything else other than less clumps of algae showing up on
> Flourite.  Seem to get considerably more pearling, looks like bubble wands
> all over the tank.  I haven't been using it long enough to tell any kind of
> long-term effects, just a couple of weeks.  Just my two cents.

Daphne, before I get into the rest of this stuff I should point out that
the pearling is from photosynthesis.  The liquid CO2 products provide
carbon to the plant without photosynthesis, so the pearling you saw was
not a direct effect of the "liquid CO2".

Seachem sent me a bottle of Excel a few months back.  I added it here and
there in a few trials, and decided that the best situation for using
the "liquid CO2" products was in a low light tank without CO2
supplimentation.  If you're already adding CO2 there isn't much point to
adding the liquid carbon suppliment.  It didn't work at all well in a
high-light setting.  I don't think the uptake rate was able to keep up
with the plants' demands.

I have a tank that has been set up for about 14 years.  The tank has
always been planted, but it has never well lit and I never gave it CO2.
Just the same, it was about half filled with crypts and java moss.  I
recently added a few more light-demanding plants (H. corymbosa, E.
cordifolius and L. cardinalis (dwarf)) that from past experience I was
pretty sure would not do well in this tank.  In the course of cleaning out
the tank and getting things ready I also found a little group of stunted,
grass-like plants tangled up in the java moss.  I couldn't immediately
identify them, but I replanted them front-and-center and they later turned
out to be dwarf sag.

I left the tank in this setup for about a month to see how things would
grow.  The crypts and java fern stayed as they had been for the last 14
years.  The dwarf sag took root, but didn't grow much and almost
disappeared again.  The recently-added plants all went into suspended

Then I started adding the Excel at the recommended dosage.  There were no
spectacular changes, but by the time I got to the end of the bottle there
were some clear differences.  The crypts (several species) in particular
looked much better - in fact looked better than they ever looked before,
with longer, wider, more ruffled leaves and deeper colors.  They also grew
faster and quickly expanded into areas they never colonized before.  The
sag became well-established, but remained stunted. The H. corymbosa held
in better than it ever had in previous attempts and actually looked good
by the time the bottle ran out.  The dwarf L. cardinalis grew slowly but
surely and looked very nice.  The java fern was pretty much unchanged and
the E. cordifolius didn't do much during the test that it wasn't doing
before the test.

I didn't have any algae problems.  In fact the tank had quit a bit of BBA
in it before the test, and that was mostly gone at the end of the test.
Some tufts of well-attached hair alge appeared in the tank, but didn't
become noticable until after the Excel ran out.

I concluded that Excel was really good for improving conditions in
low-light tanks.  I couldn't associate any algae problem with the Excel.  
However, some plants responded better than others, and even those that did
respond well (the crypts) didn't reach the size that the same plants could
reach with adequate light and CO2.  I doubt that any "liquid CO2"
product is an across-the-board substitute for added CO2 and good light,
but in a low light tank without CO2 my results were very pleasant.

Roger Miller

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