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Re: PMDD - Ratio of K2SO4 to KNO3

Aquatect2 at aol_com wrote:
> Still working out the dosage levels on my 65 gallon plenum tank.  The Tim
> Mullins mixture recommends 2 tablespoons of K2SO4 and 1 tablespoon of KNO3 in
> 500 ml of water.  I am now having to dose KNO3 separately from the other
> components and at a much higher volume to keep nitrates detectable.  Should I
> also be dosing the K2SO4 WITH the KNO3 at the same 2:1 ratio?  I gave the tank
> a jolt of K2SO4 to see if it will drive nitrates down rapidly....haven't
> measured yet.  BTW, I can't get the Seachem iron test to EVER show any
> trace....but the hair algae tells me I might have a surplus.  Phosphates are
> nil, CO2 is keeping pH at 6.8, nitrates are at about 12 (for now) so the only
> other macronutrient I can see messing with is potassium....

My personal feeling is that you should not be adjusting the potassium
higher along with nitrate if you are keeping fish. The reason for this
is that I think the PMDD ratios assume that some nitrates (or ammonia)
is gong to be supplied from fish (fish food). However, if you find you
are low on nitrates and you increase the dosing levels, chances are that
something else is going to run short. In many cases its potassium but it
can just as easily be calcium. Watch for problems with the older leaves
getting holes and turning yellow as an indication of shortage of
potassium. A critical shortage of calcium can show up as poor growth,
and twisted, gnarled new leaf formation or no new leaves at all. If
you're at this stage, I think you've already missed the early signs of a
calcium shortage.

I have found that the early signs of a shortage of calcium shows as slow
growth rates, smaller leaf sizes and a tendency for leaf melting
especially in Cryptocorynes. If you have hard water, you can try
increasing water changes and watch for growth changes over a one month
period. If you have soft water, try doubling up your calcium carbonate
dosing for about a month. 

You may not observe leaf melting except under strong lighting
conditions. I've been plagued with persistent leaf melting of several
species of aquatic plants, especially Crypts, ever since I replaced my
MH bulbs with new, higher actinic (5000K) bulbs this spring. Early on
there was a drastic Crypt meltdown but the leaf damage was not confined
to Crypt species; Aponogeton and Echinodorus horemanii leaves also
showed a tendency for leaf damage of the leaves exposed to the strongest
lighting intensity. To a degree, the plants were able to readjust to the
higher lighting and I shortened the lighting duration and moved the
lamps up a little higher. Still, the upper most leaves of most of the
Crypts and the other plants continued to show tissue damage although the
Crypt melting did not proceed to complete loss of leaf structure.

Since I learned about the possibility of a calcium shortage causing this
symptom, I've increased the dosage levels and frequency of CaCO3 dosing
and after a few weeks, I can already notice a significant improvement.
I've also noted an improvement in growth rates and leaf sizes and
health. I think I'm finally getting the tanks back to the same stable
levels as prior to the bulb replacements. I suppose my bulbs are burning
in slightly too as I suspect I could get by with much less light
Steve Pushak                              Vancouver, BC, CANADA 

Visit "Steve's Aquatic Page"      http://home.infinet.net/teban/
 for LOTS of pics, tips and links for aquatic gardening!!!