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Re: [APD] KNO3, nitrates and test kits

Just curious, what kind of nitrate test kit are you using.

If your plants were limited by factors other than nitrates,
and yo started supplying more of those things, then the
nitrate consumption would climb.  The levels can drop
quickly. It's good to dose nitrates every few days or
daily, including what you're dosing via fishfood , which,
presumably, is daily. 

That doesn't address your question, but it's part of what
is probably going on -- a heavily planted tank can suck up
10 or 20 ppm KNO3 in a day or two.

Are you doing water changes to control the build-up of
organics and TDS?

Scott H.
--- Alex Vakulenko <alexv at vakcer_com> wrote:
> Hi again,
> I have something weird going on in my tank. I'm just
> starting to use PMDD
> for fertilization in my 55 gal tank and there is
> something with KNO3 and
> nitrates which I can't figure out yet.
> I used to have about 20-30 ppm nitrates in the water from
> bioload before I
> got into PMDD. Since the nitrates are elevated, I made
> the mix without KNO3
> for now, just trace mix, MgSO4 and K2SO4. I started
> dozing it for a few days
> and nitrates went to almost 0.
> Then I created just KNO3 solution with recommended
> concentration (I used 1/2
> tbsp per 250 ml water). I doze 10 drops of PMDD daily, so
> I decided to use
> half the recommended amount of KNO3 for now and added 5
> drops of the KNO3
> solution along with 10 drops of PMDD yesterday in the
> morning (after
> checking the nitrate level being around 0). After I came
> from work the
> nitrate level was about 60 ppm (according to my test
> kit)! I was quite
> surprised but didn't do anything. Today in the morning I
> tested the nitrates
> again and they were almost zero again. I added another 5
> drops of KNO3
> solution and you guessed it, in the evening I also have
> over 60 ppm (the
> test reaction is deep red). It's seems even more than
> yesterday.
> I thought that maybe I did something wrong and created
> the solution too
> strong. Or maybe the chemicals were mixed up. So I get
> just tap water and
> added a drop of PMDD to it and tested it for nitrates.
> There were no
> detectable amount. Then I added a drop of KNO3 solution
> there. Surprisingly,
> the test kit just showed a trace of nitrate (less than 5
> ppm). Then I added
> 5 more drops just to be sure. And it showed just about 10
> ppm or so.
> Now I'm missing something. Does KNO3 release NO3- slowly?
> As K is consumed
> by plants, will NO3 ions be left and detected by the test
> kit? Could there
> be any other explanations for what I'm seeing? Can light
> play some role
> here? Can just a few plans consume 60 ppm of nitrates
> overnight (without
> photosynthesis)?
> I will test the water in the morning and if nitrates are
> low again, I won't
> add KNO3 and will see what happens in the evening
> tomorrow.
> Alex
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