Asian catfish: health and temprament
Your description matches an upside down catfish that I recently adopted - very dark solid color, 6 barbels including 2 on the nose, and no scales. It took me several days of searching the web to identify it as an Asian upside down catfish. However I was tipped off towards Mystus leucophasis by its description on PlanetCatfish of being beautiful and vicious. As for the health of your cat, I had noticed white spots on the sides of mine when I adopted him which turned out to be ich. I am a new aquarium owner, and as such have not dealt with fish diagnosis before, but I was remembering you mentioning the spots on the cat's side, and for what I've read, these cats don't develop spots until they grow older (mine is ~2 in.). Also, as a word of caution, as I mentioned earlier, these cats can be vicious. Be careful about what kinds of fish you put with this cat, as they will eat just about anything that is 3/4 their own size. When I adopted my cat, I put him in with my beta (my only other fish) and have since had to separate them in order to protect my beta. My cat would chase my beta and nip at his pretty tail, needless to say the beta would try to keep his distance - and they are essentially the same size!