swollen belly on fish

Question
I have a 6 year old 40 gallon tank with standard filtration plus a bubbler. I do 25% water changes about once a month. There are several cichlids and 1 whiskered catfish. A few weeks ago the catfish developed white spots on it and I treated the tank with Permafix for 7 days and then did a water change. The spots went away and 2 days later the belly of the catfish swelled up overnite.(the cichlids did not have any white spots.) Its appetite has not changed and it has no difficulty swimming. It has now been about 1 week since the belly swelled. I don't remember what kind of catfish it is. It's 5 years old,about 6 inches long, dark charcoal grey with white underbody, no gills and has small eyes and whiskers. It was a pet store purchase. It does like to munch on other fish. (It ate piece by piece a goldfish my kids put in the tank about a month ago) and will attempt to eat any other fish introduced into the tank. It does not bother the cichlids. My daughter thinks it's pregnant,but, unless catfish reproduce by immaculate conception, I don't see how it could be. If you have any idea as to what can cause a swollen belly in this catfish, please let me know. I appreciate your time in reading and responding to my rather lengthy question. Thank you and look forward to your reply.

Answer
Swim bladder disease.

Copy and paste this into your browser.

http://www.aquaticcommunity.com/disease/swimbladder.php

Also, just type in swim bladder disease on google, and you should get 100 hits.

All the info you'll ever need is out there, you just need someone to poitn you in the right direction ;)