Macro solution with KHCO3 - The Planted Tank Forum
 
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post #1 of 3 (permalink) Old 12-03-2015, 10:27 PM Thread Starter
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Macro solution with KHCO3

Hello, I'm going to make a macro solution with KHCO3 as a main K source. I'm doing this for various reasons. My water is extremely soft, and ADA aquasoil sucks up all the bicarb.

My question is will these salts be okay together in aqueous form in 1000mL of water? Each dose is 30mL

KHCO3 (enough to add 3.2 ppm K and 0.23 KH per dose. 72g in 1000mL of water)
KH2PO4 (small amount, 0.2 ppm per dose)
KNO3 (enough to add 1 ppm per dose)
Urea (CH4N2O) (enough to add 0.5 ppm per dose)

I'm pretty sure KH2PO4 and KNO3 are fine with KHCO3. My main concern is the Urea forming NH3 and combining with the bicarbonate in some way. I looked up a possible reaction and found that these two things could make ammonia bicarbonate or ammonia carbonate. Both are which are very soluble in water. Almost as much as the KHCO3.

Any chemists around here?
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post #2 of 3 (permalink) Old 12-04-2015, 01:58 PM
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Is there any particular reason you are adding urea instead of relying on the potassium nitrate to provide the necessary nitrogen?

Urea will indeed break down into ammonia, and may or may not become toxic, depending on your pH.

Anthony


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post #3 of 3 (permalink) Old 12-08-2015, 04:32 AM
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Quote:
Originally Posted by Darkblade48 View Post
Is there any particular reason you are adding urea instead of relying on the potassium nitrate to provide the necessary nitrogen?

Urea will indeed break down into ammonia, and may or may not become toxic, depending on your pH.
Ditto on the urea. Its completely unneccessary IMHO. Other than that the chemicals you list are compatible with each other (yes, I am a chemist).

I currently use potassium carbonate as a K supplemental source. The thing to keep in mind is that carbonate will buildup in water rapidly raising the KH. Monitor pH and KH on a regular basis until you figure out a steady schedule.

I use anhydrous citrate as a acidic pH buffer to counteract the carbonate excess when needed. Citrate will react with excess carbonate to drop the KH and release CO2. Citrate is also an excellent carbon source for beneficial bacteria in the tank and does not accumulate.
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