what's wrong with my catfish?

[prowler09]

I have a silver tip shark catfish, he is several years old and bout 8-9 inches long.
Over the last couple days he has been acting wierd. He's been swimming around rather awkwardly, and upside down most of the time. He will sometimes go to the top of the tank and kinda flop around while swimming. He also doesn't seem to be able to close his mouth. My dad said it looks like he has to keep moving to get any oxygen. I don't know what is the matter. He has never done this before. Im afraid he may be on his last leg, so to speak. Does anyone know what is wrong and what I can do to help???
Thanks in advance.

 

[prowler09]

...by the way, he is in a 55gal aquarium with an oscar and placo who seem just fine.

 

[Bsixxx]

i heard that they are actually brackish fish

so thats probly why hes freaking out

 

[davo]

Yeah, they are brackish from what i remember.

 

[prowler09]

yea i knew they were brakish, but he has been living in this tank for 4-5 years no problem

 

[prowler09]

...and if he is stressing out because of that, should I add any aquarium salt? How much? What about the other 2 fish?

 

[Bsixxx]

a tbl spoon per every 5 gallons
or something like that

 

[prowler09]

will it bother the other fish?

 

[Bsixxx]

are they brackish also?

 

[dragonfish]

Regular aquarium salt may not help. What are the water parameters? Would be better with marine salt or at least the mix for africans. That would be more acceptable to him but uncomfortable for your oscar.