last week i noticed my goldfish acting very strange.. 1 lay stil at the bottom, another hid its head in a rock, 1 even flipped itself out of the tank! i thought why is it my fish seem to b trying to commit suicide!! looking closely, i noticed their fins were frayed, 1 in particular.. after research on the net, i found out my aquarium had high ammonia levels and the fish were trying to escape from the polluted water as it was burning their poor fins!! .. i panicked and immediately did a full water change, even invested in a new larger filter adequate for the tank size, and bought a plant to allow more oxygen into the tank! thank goodness it seems to have done the trick! the sickest fishs fins have now turned black on the ends.. a positive sign of healing they now look alot happier and healthier.. ammonia is caused by a build up of fish waste/rotton food, i am now going to get an ammonia tester so i can keep a close eye on the water quality and am going to get an aquarium vacuum to keep the gravel clean.. i know the money adds up but its a small price to pay to keep my fish healthy!