I purchased a 90 gl saltwater aquarium 1 month ago from a guy who had it for 2 years. I have kept an eye on the water conditions and everything is perfect. I even brought a sample to the local store and they told me that they wished everyones water looked that good. Since then I have had three fish die and my star polyp has not opened. I have had an ich problem with a couple of fish and have been medicating the aquarium. I don't know if this is the problem, but the store told me it would be fine for everything in the aquarium?