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Re: PMDD - Ratio of K2SO4 to KNO3
>>>>> Aquatect2 <Aquatect2 at aol_com> (here: "A"),
>>>>> on Sat, 3 Oct 1998 12:01:18 EDT,
>>>>> pondered the meaning of life, then wrote down:
A> Hi All,
A> Still working out the dosage levels on my 65 gallon plenum tank. The
A> Tim Mullins mixture recommends 2 tablespoons of K2SO4 and 1 tablespoon
A> of KNO3 bin 500 ml of water. I am now having to dose KNO3 separately
A> from the other components and at a much higher volume to keep nitrates
A> detectable. Should I also be dosing the K2SO4 WITH the KNO3 at the
A> same 2:1 ratio? I gave the tank a jolt of K2SO4 to see if it will drive
A> nitrates down rapidly....haven't measured yet. BTW, I can't get the
A> Seachem iron test to EVER show any trace....but the hair algae tells me
A> I might have a surplus. Phosphates are nil, CO2 is keeping pH at 6.8,
A> nitrates are at about 12 (for now) so the only other macronutrient I
A> can see messing with is potassium....
Stick to the Sears-Conlin approach. If your NO3 is being consumed to 0, then
nothing else is limiting, so don't dose more K2SO4 or micronutrients until
NO3 stops being completely consumed. This will drive your iron to the proper
levels. If you're positive you have 0 phosphates and you have hair algae, then
you could be dosing too much iron. I'd say "test your phosphate kit", but in
my experience, hair algae is not the dominant algae that shows up when you have
measureable phosphate levels. Someone correct me if they've seen otherwise.
But *something's* consuming your nitrates, and if it's not also consuming your
iron, you might get recurring hair algae problems. If you have 0 phosphates,
then your plants aren't consuming any more iron and you'll have to add
phosphate to help them consume it, or add some plant that can do the job
without the phosphate (duckweed? doubt it). If your plenum's absorbing all
those nitrates, it's going to keep your plants from absorbing the iron and
will be competing with them for NO3. Watch for deficiency symptoms of some
kind in your plants to see if this is really the case. The other thing that
it could be is that the hair algae is temporary and it's already dying away.
Give it a couple of weeks to see and make sure your nitrates are always
measureable to reduce the instability that's promoting the hair algae.
My Seachem kit's always had problems with chelated iron. I've never been able
to measure iron in my tank. I infer iron levels from the presence of hair
algae, the absence of other algae, and measurements of macronutrients.
Just in case, test your nitrate kit on a dose of your KNO3. Just to be sure.
Carlos E. Munoz
<cmunoz at crystal_cirrus.com>