out of all the fish i have had i would say my male jag was the meanest, with a blackbelt in close second. but overall try putting a new fish, anysize, in a 10" or bigger jardini's tank.
a redtail catfish just eats and eats and well eats any thing there as they say theres on 2 types of fish in the world a redtail catfish and a redtail catfish'es food !!!!