Floating upside down catfish?

[luckypenny]

I have a newly set up 75 gallon tank and have had it setup for 1 week now. I have a upside down catfish along with two clown loaches and a two bela sharks. All fish have been doing fine--but my catfish the last three day's floats to the top of the tank. I try and catch him and swims to the bottom barely and hides in a rock?? Does anyone know the cause of a floating fish??
Should I take him out to keep the other fish from getting sick??

 

[squidlips]

ither swim bledder ..air gets stuck in its tummy . if you grab a litre of water from tank in a dish add fish 1 tspoon epsom salts leave 10 min . return to tank should work .

 

[lady_tanksalot]

is this a totally new tank? have you done any water test? if so what are the levels?