I need help!!! Cycled tank readings nitrite 0 ammonia 0 nitrate 20 added betta 2 shrimp and a few days later a long nosed snail. I do 2 30%w/c a week and reading are nitrite 0 nitrate 20 and ammonia 0.25 why do I have traces of ammonia can some one help me? btw all inhabitants are showing no...