We have had our 55gallon tank for going on 3 months now. We have right now a Yellow tang, clown fish, gobi, and somet crabs. We have ordered all the clown fish off the internet. And out of 9 clown fish one has made it. And now he isn't doing well. Swimming around like crazy and doing what the others started doing before they died. We have not changed anything for a while now. And he was eating really well but now he won't eat at all. We are new at this saltwater aquarium thing and we love it. But I don't like the fish dieing. My yellow tang has something on his gills and he turns pale yellow sometimes. We have already cured him for black ich and he doesn't have anymore. So. I don't know what is going on. We have checked everything in the tank and it all is good. The only thing we haven't check for is Copper. Please help.