Phatboy said:red tailed cats can be housed in a reasonably big tank.
paroon sharks are another story. they grow big, probably up to 4ft. Not only that, but they are active schooling fishes, which means they are constantly in motion (unlike the red tailed cat). In order to house such a monster properly (multiple of them, actually), you will need a tank size no smaller than your livingroom.
Speaking of paroons..When I went to my LFS on sunday they had a 20" one in their big display tank. They had no idea what it was so I told them it was a paroon shark and that it was a type of catfish that would reach 40" at a minimum.. They owner freaked and told me I could have it a half price..I turned him down..I really do feel sorry for the fish though..I hope it finds a decent home..