Ok this one has got me perplexed.. One of my tanks, a 10 gallon, has been cycled for two months now. All levels were fine. Then last week my ammonia was off the charts. I assume most ammonia's testers are alike and go from yellow to green, and mine was dark dark blue. My nitrite was 0ppm and nitrate at the normal 20ppm when I was about to do the water change. I changed 50% of the water and treated with AmmonLock sp?... This week same thing, and another big water change. The fish seem fine, there are 2 gold barbs, a small red tail shark and 4 two month old Mollies. Any thoughts??