Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
The second group of bacteria, the ones that remove nitrite are very slow growing.
They do not mind it if the NO2 approaches 5 ppm, so your level of 2 ppm is not a problem for them.
Still, you could do a water change just in case the many species of microorganisms and the plants have used up some mineral or salt that they might need.
Raising the temperature can make them grow faster. Make sure the oxygen level is kept high, too.
Think about this:
You are adding ammonia daily.
The plants use some, and the first population of bacteria are turning some of it into nitrites.
But the nitrite level is not rising.
So some of the nitrite IS getting turned into NO3. Or the plants are using it. (Yes, plants can use NO2).
But the NO3 is going down (no matter if it comes from the tap water or from the ammonia>nitrite>nitrate bacteria. It is getting removed by the plants.
Anyway, yes, the nitrifying bacteria are still growing. Give them the optimum conditions to grow as fast as possible, and the cycle ought to be complete pretty soon.