Hello. I have just recently started my first fish tank (55gal) in december. I evenetually bought two tiger oscars, 1 red hook, in Jan. i also have 2 cat fish, and two pelcos. I noticed that the red hook was swimming sideways, the best diagnosis that i have come up with was a swim blatter infection and i treated him with an antibotic. he still swims like that once in a while but immediately swims normal at feeding time. I change the water at least once a week and i don't know if that is two much or two little my concern is that im doing something wrong. last weekend i noticed that one of the oscars was swimming weird as well so i did and emergency water change and it seemed to help my main problems seem to be nitrates and Ph if anyone has any suggestion it would help me out.. you can e-mail me reluctantrenegade50@yahoo.com or IM me at farmer22348 thanks