Fish Staying at the Top of the Tank

Question
We have a 37 gallon fish tank. Inside of it we have a small bass, a small blue gill, some feeder fish, and three small catfish. All of the fish except for the catfish are swimming up at the top of the tank at the edge of the water. It appears that they are trying to get air, but our filter seems to be working just fine and the catfish have gone up to the top once. Do you know what the problem could be?

Answer
Dear Corinne,
Thank you for sharing your tank situation with me. It sounds like they are sick. I recommend that you read my page about aquarium care:
http://steamboats.com/aquarium.html
and follow the instructions for "emergency in the tank" at the bottom of the page.
Usually fish get sick from over feeding because it pollutes the water. The most important thing is to stop putting food in and get some organic biology (Cycle) to break down the poisons.
I hope this helps. Write back if you want to discuss further.
Nori