i have a catfish... dunno what type it is tho, but its about 8 n half inches long.. all it wants to do is sit on the the bottom, and swim though my plants and goes crazy at feeding time, but i have Ruby sharks currently 2, i uset to have 4 of them all in the same tank they all got to at least 6inches and they uset to group together and rub up against each other... they havent been agressive towards my catfish in anyway, but they seem to chase my silver sharks but never do any damage.
Ruby sharks are exactly the same as a red tail but i think they look abit nicer.
Hope this helps