Stephen Henning wrote:

Ammonium compounds and Ammonia are two different things just as Salt
(sodium chloride), Sodium and Chlorine are very different things.
Ammonia is NH3 a very caustic gas that produces NH4OH a caustic alkali.
Ammonium compounds are salts frequently used as fertilzers.

They're only different until you dissolve them in water. Then there is
a pH dependent chemical equilibrium between ammonia and ammonium.

NH4+ (ammonium) -- NH3 (ammonia) + H+ (protons)

At the 7.5-8.0 pH ranges typical of koi ponds, the ammonia, ammonium, or
whatever you want to call it is partly in the toxic NH3 form.

Looking at water lily fertilizers we find that many contain ammonium
compounds. For example:

CrystalClear Aquatic Plant Fertilizer: 5.5% nitrogen from Ammonium
Phosphate.

Tetra FloraPride Aquatic Plant Fertilizer: Ammonium Heptamolybdate.

Most water lily fertilizers are designed to not contaminate the pond
with nitrates and phosphates. And the bacterial breakdown of urea
creates ammonia, so most fertilizers do actually use ammonium compounds.

Just because you can buy something at a pet or garden store doesn't mean
it's good for fish. Most fishkeepers underestimate the extraordinary
toxicity of ammonia to aquatic life. Pure nitrate, on the other hand,
is easily tolerated by fish in the ranges appreciated by plants.

Also, this thread started with bare-root lilies. If the pond isn't
"contaminated" with nitrates and phosphates, the lilies will starve.

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