About a month ago I noticed that my sucker fish started floating upside down a lot. I almost thought he was dead but when I tapped the tank he moved. He has been doing this amost all of the time lately. He is about 5 1/2 - 6 years old. Is it just that he is getting older or is there something wrong? That might be a stupid question, but I really want to help him if I can :) Thanks!