What are the params? Ammonia, nitrite, nitrate? Numbers? How long have these animals been in this tank? What type of filtration are you using? I'm not trying to be mean. This information is actually important. You can keep adding medication, because it makes you feel better, or you can get some real answers. Honestly, some of the employees at Petco could put their information about fishkeeping in a thimble. For one thing, buy your own test kits. For another, ask for NUMBERS. What they think is "fine" may not be what is actually "fine." They're your fish, and you want them living by your standards, not some know-nothing employee of a chain store.