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Re: Ammonia vs nitrate

Research to date indicates quite clearly that submerged aquatic plants
prefer ammonia over nitrate... in fact plants that have been tested wont
even take up nitrate until all the ammonia is gone. This is sound
strategy, since ammonia is already reduced, while plants must expend a
great deal of energy to reduce nitrate before it can be used to make
amino acids. This fact is one of the reasons why a reduced substrate
(anaerobic, anoxic etc.) is beneficial in a planted tank... aquatic plants
can then take up ammonia directly from the sediment via their roots.
Aquatic plants will, however, exist quite happily on a steady diet of
nitrate. (This is similar to the carbon dioxide/bicarbonate debate... all
aquatic plants that have been tested prefer straight CO2, but about half
of all submerged species will also grow quite well using bicarbonate as
the carbon source... this again is a sound strategy considering that at pH
7 about 80% of DIC is in the form of bicarbonate).