I think that a Betta would do the trick. They love to snatch anything up that will fit in their mouth. I got one and almost all my fry are gone. I must've had a couple dozen. Even my eel wouldn't eat them.
Would a Betta really be ok in a community tank like this? My girlfriend LOVES them but from what Ive read they will tear up everything in the tank. Id love to be able to throw 1 or 2 bettas in there but I dont want them to mess with my gourmami's and especially the angels.