I started my 20 gallon tank, which was an upgrade from 3 gallon tank with guppies, 1ballon Molly, 2 Mickey Mouse platyies and a dwarf gourami, and a otto for algae control. I understand that I am going through the nitrogen cycle and my ammonia level has ranged from 0.25-0.50 and would do water changes at least once a week, some times 2-3 depending on my ammonia level. So I see the light at the end on the tunnel when my ammonia dropped to zero, nitrites are zero but my nitrates at between 60-80 and what has resulted? A bacteria bloom. So through the sea of googling I'm finding mixed responses to this. Should I treat this or just watch and wait? I just did a 25% pwc weds. I have the API master kit along with a sea chem ammonia detector in my tank. First time I've seen that pretty yellow! I thought it was a fluke! I did test my tap water for nitrates and it is zero so that's not the problem. I haven't lost any fish and they seem to be doing fine.