I have a 55 gallon tropical community. It has been understocked for a while now, so last week I went to the lfs and got 5 new fish. They were 2 rosy barbs, 2 buenos aries tetras, and a gold nugget pleco. Like a moron, I didn't quarintine, and now I have major problems. On the 2nd day with the new fish, I woke up in the morning to find one of the new barbs dead with mouth fungus(that I didn't see before putting it in the tank). It was immediately removed. When I came home from work, the other barb was dead along with one of the tetras. Neither one had any visual problems. Now, I am losing one to three fish a day. It started with the smaller ones, like the platies, barbs, tetras, etc. now it seems to be affecting the larger fish. This morning one of my 9 inch bala sharks was dead. The fish breath heavy for a day, won't eat, are lethargic, and dead the next day. Now, one of the tinfoil barbs (6 inches)is breathing heavy, so I expect it will be dead tomorrow. I have done 2 50% water changes, added salt, upped the heat to about 88, and have been using melafix. Nothing seems to be working. Other than the heavy breathing, there aren't any other symptoms (the fungus hasn't shown up on any other fish). I dont know what else to do. Water parms. are all normal. The few fish I added were so small, I didn't even see an increase in amonia. Any suggestions?