Thank for the help. I hope you got a minute. I inherited a 75 gal tank when I bought the house in July. It came with a adult 3 spot damsel(the bully), blue damsel, clown, and a 3 stripe damsel(who died last week) using a wet dry filter. The kids wanted more fish so I went to LFS and asked his advice and he had good priced fish. I came home with Coral Beauty and a squirell fish. I wasn't told that i should qt the fish before into to my tank, well the bully damsel took out his fustration out on the squirell and constantly picked on him. A friend told me to keep the tank covered in darkness to give the squirell a chance. It worked. Approx 3-4 weeks later I bought a lunar wrasse(my fav)and a butterfly fish. 5 days later the squirell fish was attacked by the wrasse, then he took out the coral beauty. I was so pissed that I took the wrasse back to the LFS and asked for a refund or return. I didn't know he needed more meat in his diet. Well he took him back gave me a free bag of salt and sold me a nice butterfly fish for $20. Everybody was doing fine, then all of sudden the butterfly was starting to swim sideways, rubbing, and swimming in the stream of the water return. 2 days later, He was dead. I removed 25 gallons of water, cleaned the tank and replaced the water with the proper salt added. I checked my water for ph, am, nits and all was in good conditions. I usually changed the filter in the w/d every 10 days or so because it got clogged and send air into the tank and clouded it. My friend suggested that I add more filtration because my tank was not as clear( and still not), ---- here I come. I bought a new Fluval 303 and it installed it with act char and blue filter pad I couldn't help it I bought a yellow tang for $20.. The temp dropped in jax but my tank stayed between 75-80. Then the 3 spot started acting like jaws, swimming with his fin out of the tank, swimming up in the stream, like he was tring to cool off. The clown started to develop a fuzziness around his face. Then it really got cold. the tank temp went to 70. 3 spot was really in trouble he was breathing faster, he would go to the bottom and fan the sand with his body, swim sideways then jet around like he was ok. when he would slow down the clown, 3 stripe would swim right next to him really strange like they knew he was dying. The next morning he was face down. I bought a heater at a bigger LFS. I told the owner everything I am telling you and he says that a fish could have had a disease of ick or velvet and it didn't make it self known unil the temp went down. he says that the fuzziness soulds like velvet and suggesteted I by cfx(copper) and treat the tank with it every 72 hours and heat the tank to 82 l. ok. I went back to my first LFS and he sold me some more blue stuff called quick cure(formalin)to treat the tank daily and lower the temp to 78. I removed 25 gallons of water, cleaned the tank and replaced the water with the proper salt added. I checked my water for ph, am, nits and all was in good conditions. The fish seemed happier that the temp is ok and the fuzziness on the clown, 3 stripe started to go away. Then I see a the growth on the clown and I wonder is that a zit? Update: 3 stripe damsel did the same thing the 3 spot did before he perished so I was going to take him out the next day.... didn't make it. Last night Yellow tang same M O . Died today... Who next? I think clown or blue damsel.... What is going on? I realize I killed the fish by going to fast but how can I stop the deaths