First off, Hello everyone after lurking on many sites since I started this hobby with my Fiancee a few years I figured I'd finally register!! We have a problem. Fish keep dying, and we have no idea why. For about the past 6 months putting a new fish in the tank has been a 50/50 chance that they will live. We keep the salinity at 1.024 (why I don't know, my fiancee is the expert) and we do water changes regularly. The fish that we get will usually live for 3-4 days before they just dissapear. Until recently. We went to PetCo and got a Tang, Angel, and 4-5lb of new rock that came out of the same tank that the fish were in. What kind exactly, I'm not sure. The Angel lasted 1 night, was dead the next morning. Several days after this, my fiancee noticed what she thought was some bubble algae in a corner of the tank so she put in a treatment that we had in the chemical cabinet that would combat the algae. The next day, the algae was still there and the instructions said to apply one treatment per day until the algae was dead, so she put in a second treatment. That night, the Angel was appeared to be drunk. The fish would just flop around in the water and would come to rest at the bottom of the tank like it was laying down. If you put your hand in the tank, it would swim vertically up to the surface of the water and just bob there. Eventually it would fall to the bottom of the tank again. The next morning it was dead. This left us with 1 Clown fish and 1 black-pink blenny (they have been in the tank for several years). We then took a sample of the water from the tank and a sample of the water from the tap (since we use tap water to do our water changes) up to PetCo and they ran all the usual tests that we do, Alklinity, Amonia?, Nitrates and several others. They said that both samples were clean and didn't show anything unusual. We purchased new carbon filters and put them in and let the tank This left us with a Clownfish and a black-pink blenny. We let the tank sit for 3 weeks, just feeding the two remaining fish and letting the water try to purify itself with the new filters. 3 days ago, we went to Petland and got 2 black clowns and a Mandrin Dragonette, all of them were swimming around just fine, we brought them home and acclimated them properly. They have been doing fine until this morning. One of the black clowns is almost dead, and the other looks very bad, both have the same drunk-style swimming. Does anyone have any suggestions as to what is going on? And whatever the reason is, why isn't it affecting the fish that we've had in the tank since all this began. I just find it hard to believe that all 4 fish were sick before we brought them home.