Why not widen your horizons a bit? There are lots of great fish that aren't "predatory" in the traditional sense, but are still really fun to watch. My silver dollars go into feeding frenzy mode when it comes to flakes, and you could easily keep some spotted ones in a 55. They jump all over the place, splashing and going crazy. With them, you could still add some other bottom-feeders for activity all over the tank. Feeding feeders is something that most people who know what they're doing and understand the effects of their actions try to get AWAY from, not work toward. Possibly some more research before you buy?