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Re:Plant tabs, PO4 and Miracle Grow

> NOW, I have never used them, but I traded Mike T a
> slew of Micranthemum for a 100 tabs, and I should go
> over and pick them up. The breakdown of this fert is
> *well* documented in The Krib, but I've not heard
> anyone speak of them on the list since I have been
> subscribed. Does anyone have *any* experience with
> these things? 

I used them a few years ago. They seed good, perhaps as good as laterite
balls. Not bad stuff IMO.

> My only problem with these is that he has his "family
> secret formula", and doesn't list the ingredients.
> Isn't that illegal? They don't appear much different
> than Miracle Grow.

Fe, Mn etc hey, make your own if you want. Perhaps I'll try that:)
I do not think they have NO3/NH4 or PO4.
Jobes could easily take the place of that. Illegal:-)?


Neil wrote:

> Ever since the discussion on PO4 additions started 1-2 years ago, I have
> used Miracle Grow (the blue crystals) to occasionally supplement my tanks.

So was it the NH4 and urea or the PO4 that helps your plants? Urea can be
quickly converted in the presence of water and oxygen and bacteria into NH4
and used. Can you see what 1.0ppm of PO4 is like without problems associated
with NH4/Urea? How about 2.0ppm of PO4?

> The actual percentages of N, P and K by weight are 15%, 13.2% and 12.5%.

So how much NH4 vs PO4 is there here? Try a .5ppm level of PO4 and a .4ppm
NH4. See what that will get you. Not bad for tiny extra amounts but at high
PO4 uptakes which I've seen in my tanks and other this PO4 will become PO4
limited using this. Other wise toxic NH4 levels will be reached.

>Here are some dosing possibilities:

> 0.2 grams of MG (15-30-15) in 70 gallons of water will yield a Phosphorus
> (P) concentration of 0.1ppm. [This corresponds to a PO4 concentration of
> 0.34.] I have not yet used higher ammounts.

This limits investigation of higher PO4 levels since you will get
correspondingly high NH4 levels. I'd say that even using this MG or Shlutz's
etc you will still be PO4 limited.

 I have found no good evidence for having a PO4 limited planted tank
personally if you add CO2.

Isolation of each component will detail the underlying causes of good plant
growth and the suppression of algae. But M.G. and Shlutz's are not bad by
any means. They do have short comings and problems. KNO3, K2SO4 and KH2PO4
have less though. This gives individual tailoring of each primary macro.

> It was the most convenient source of P that I could find, and because it
> was already in the house, the price was right :-)

5$ for a pound of KNO3 and a lifetime supply of PO4 is about 10$. MG was
about 4$ for a life time's supply. Certainly worth a try! I added it to my
little pond but the Racoons ate everything. Seemed to work pretty well in
small doses. It certainly brings up ideas about trying richer and more
improved plant nutrition.


 Although the mix has
> other plant nutrients (including Cu and other trace elements), I had to
> check to see if I might overdose something I did not want. Not the case --
> the MG is dominated by P.... at least relative to the nutrient requirements
> of aquatic plants. For example when you add enough MG to bring P to 0.1ppm,
> the corresponding additions of N, K, Fe and Cu are also +0.1ppm for N

What kind of N?  
5.8% ammoniacal
9.2% Urea
The forms of the ammonia are Urea and ammonium phosphates and urea
phosphates.

Plants have rough time using Urea. It needs broken down by bacteria. So
there's some lag time before this used.

But algae can use organic PO4 by using alkaline phosphatase that allows
algae to use it and store it as a luxury nutrient where as the plants need
bacteria to do the deed. So if adding inorganic forms of PO4 such as KH2PO4
will even up the selection for the dynamics between algae and aquatic
macrophytes. Algae can live up to 20 generations with a healthy storage of
PO4 granules at absent PO4 levels. Your plants will be in sad shape and rot
and decomposition of plant matter will add enough organic PO4 back into the
system where the algae have the advantage. Adding inorganic PO4 may
circumvent this process. Not sure but will look into the literature more.
Sounds better than some of the other ponderables.

Although urea is an organic N fertilizer, it is rapidly converted to the
ammonium form within a short time after exposure to aerated water and
bacteria. Therefore, under most conditions urea acts more like inorganic
ammonium fertilizers than like natural organic fertilizers. It's also cheap
stuff(Moneywise).

> To complement the P, I also add N and K in proportion to Gerloff's 1975
> published "critical concentrations" for Elodea which Diana Walstad includes
> in her book. The critical ratios of N:P:K are 11-2-8. [These are said to be
> minimum concentrations needed for unrestricted growth.]

Is using one species as a ruler good for all plants? Many plants are
sensitive to low levels or need higher levels of PO4 , NH4 vs NO3 is another
issue. Plants absorb P primarily as the H2PO4 - and HPO4 = ions which are
predominant. The H2PO4 - ion is more readily absorbed than the HPO 4 = by
most plants. In young plants, P is most abundant in tissue at the growing
point. It is readily translocated from older tissue to younger tissue, and
as plants mature, most of the element moves into the seeds and/or fruits.

I think the cheapy fert's from the stores are good to use though, just in
very small amounts in "lean" tanks. KNO3 and other forms of PO4 may also be
used on top of that.
My tanks slop up .1ppm of PO4 in less than 12 hours. A hungry tank should
remove it in less time.
Using cheap fert's is much more dangerous than using KH2PO4 for PO4 dosing.
It's good if your interested in adding NH4 to a hungry tank...........

> To provide the
> extra N and K not available from the MG, I use nitrate of soda (NaNO3) and
> potash (KCl). You can also use potassium nitrate (KNO3), but this does not
> provide enough N by itself.

Depends on what species of N. It does add enough NH4 for the tank.

I have considered making stock solutions of ammonium sulfate so I can
explore the independent effects of NH4+, NO3 and PO4. I have looked at it
from the dry additions but have not come to any recommedable amounts yet.
Cost is very cheap for ammonium sulfate also, 4$ for 25lbs.
I know what happens at slightly higher levels of NH4 that persist for any
length of time. Algae. It's fine if the NH4is very low and the plant growth
is dense and fast/healthy.
 
> Of course fish food will also provide N and P
> in a ratio of ~7 to 1, so the extra N may not be needed. Same about P. YMMV.

You'd have to feed a lot of food to do this in a CO2 enriched tank with
higher lighting. And as you add more food you get more urea and NH4. These
will cause algae as you increase the feedings or bioload. This also
increases the O2 usages (lowers O2 from bacterial decomposition and from
fish respiration and adds CO2).
Overall I think use of MG/Shlutz's etc are good for the lean tank with low
fish loads at very small amounts(about what Neil is shooting for at .1ppm of
PO4) with the additions of KH2PO4, KNO3, traces and K2SO4 to raise the other
nutrients up to a higher levels without letting the NH4 get out of the
control. I think that the additions of more NH4 may help the tank if it's
NH4 poor(like most well run plant tanks). I say poor instead of limited
since the plants/algae can use the NO3 also which is far higher
concentrations. Glad to hear ya Neil!

Regards, 
Tom Barr