I just took the Id shark to my LFS today (he still wasnt looking good). The owner tested my water for nitrate and amonia levels and they were perfect =) I also dont think it was the air as I have a Emperor 400 running in my 29 gal. as my bf says, its like putting a V8 in a civic, I mean I have waves at the top of my tank! The fish love it though, they swim about in the current all the time. Anyway, to the point here, turns out that little sharky had a infection, a slight cut near one of his fins and it was stopping him from swimming. He is now going to be treat and made all better =)