Cat fish starting possible injury

Question
I have a 35 x 15 foot koi pond. In it I have an 18 to 20 inch white catfish. Recently he got caught in the skimmer and I am not sure how long he was in there. I can assume that he struggled to get free. I took him out and returned him to the water. He went to the bottom. He will try to swim but he will move his body like a snake to get started and will swim for a very short time and will continue to go to the bottom and stay. It has been three days and today he turned and was upside down and then turned himself upright. I have read that he either his swim bladder is infected or damaged. Assuming that it is damaged is there anything I can do for him. He is about 6 years old.
Thank you

Answer
John, what an unfortunate incident. Yes, swim bladder does share the same symptoms your catfish is displaying and yes there is medication that MAY help, unless it is too progressed. Most pet stores will sell meds that will treat a wide variety of diseases infections and/or viruses. Go for it if you believe this is the problem. You've had em too long to not try to save him. Also, being caught in the skimmer I'm certain put it through high amounts of stress which alone can be fatal to fish. In turn, stress makes fish more susceptible to diseases and such. Also, I'm sure he lost a lot of electrolytes and vital nutrients which drained him all the way around and aided in its odd behavior and the possible infection. Its hard to say EXACTLY what the diagnosis is as I am not there, and as I mentioned before, many sicknesses share some of the same symptoms. I hope I helped a little. Good luck and keep me posted.