I agree. Discus are difficult to grow out properly in community settings. Unless you are familiar with discus, it's too easy to miss the "obvious" until it's too late, and are having problems. I have kept discus for many years, and I still grow them out in separate tanks. They grow better and faster that way. Also, I would be suspicious of anyone selling discus for $15 unless they are quarter size or so. It's a good idea to always buy discus from reputable breeders or resellers who specialize in discus, even if you have to order them online. This is especially important for the novice who has little to no experience at choosing healthy stock. LFS that sell discus often have questionable and stunted discus, and buying such fish often leads to disaster.