Lol, I kept some pumpkinseeds when I was little caught them when they where about 4" long had like 10 in a 55g, they where cool, they go into a feeding frenzy like my piranhas, if they had some big teeth they would be wicked.
Bluegills would be good, maybe small crappies, or some catfish of some sort. I had a blackbull head growing up with some of my moms guppy's who seem have disapeared.