My polypterus senegalus which grew from 2" to 8" in about 6 months, has been sharing a tank with a mess of guppies and now swordtails. For a long time it ate very few of the guppies even (it's a heavily planted tank with lots of floating plants though). I put the guppies in there as feeders hoping the plants would let enough survive for a while - which did work up until lately when it got to its current size. And, it has recently eaten a tetra or two. When it was in a more varied community tank it ignored the faster tetras and a big angelfish (surprisingly with those long pectoral fins), but it did chew the fins off a betta which was dumb enough and slow enough to get right in miz bichir's face while they were being fed. Anyway now that it's this big it's clear that that big mouth can fit bigger fish and she's got enough muscle to speed up and catch the smaller ones. Unfortunately I need to re-home the Beast because I can't afford the time and space for a 50 gallon which I think it needs at this size. I knew it would grow big but sadly must part. It's in a 29 gallon tank and getting restless! Beautiful fish and utterly fascinating to watch. Someday I'll get bichirs again. I hope to sell it to someone who has a 50 gallon with big tankmates. . .I was reading this thread to see what to watch out for.