Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Too much ammonia. Do a 50% water change. The goal is 5 ppm ammonia until the nitrites show up, then allow it to drop to 3 ppm and maintain it there with no more than once a day additions of ammonia.
These bacteria do not grow so fast when either ammonia or nitrite are over 5 ppm.