tigerlily

ok, yesterday i came home to a black moor that was floating directly above the filter and doing sideways somersaults, so i took him out and put him in a separate tank and within 20 minutes he was dead. after this i ntoiced he had a kind of white film which looks like mould all on his tail and round his mouth but nowhere else. i have come home today and the same stuff is now covering one of my orandas and the bogwood i have in the tank, i took the wood out and have cleaned the mouldy stuff off and taken the oranda out but dont know what else to do. all the fish shops are closed, would salt be a good idea and will it hurt my algae eater??? please help me soon!!!! :-?