Here's my story. I have a 20 gal tank, with no filtration, just water movement, with a percula clown and a damsal. Until about a few days ago the fish have been relatively active(rush the front of the tank when i enter room). I assumed it may be the ammonia, so i tested and the test said it was HIGH. water change...tested again right after..HIGH..water change...the fish have since been a little more active, but not as. I have limited the # of hrs the lights are on thinking it might be the temp. I also increased surface agitation to help with som 02. Does any body have any suggestions? Thought?