Can decaying plants cause a huge ammonia spike? According to my master test kit my 20 gallon is running at 8.0 AMMONIA. And has been for over a week. I've been doing daily/every other day %50 water changes with no change in levels. Nitrites and nitrates are good. So I'm confused. I have three dwarf gouramis in this tank right now and I'm so worried they may die. The only thing I can think that would cause this spike is that I found that my pothos cuttings were rotted. So I took them out. But can decaying plants cause THAT much of a spike?