Clarias Gariepinus is easily available and dirt cheap in my country. Few years back, i kept 3 of them and what an experience that was! I had them when they were very tiny, about 1.5cm. Within 3 weeks their diet had progressed from flakes to bloodworms to small goldfish pellets to carnivorous pellets to swordtail feeders--that's how fast they can grow!! depends on how you look at it; they can be aggressive and very destructive. But if you are dedicated, have a huge tank for them and the energy to match, i think they are great fishes to keep because they are so hassle free--they can survive in any water conditions and eat everything you throw at them!! Cheers!