Patrick,
You'll find that the male minnow takes on a very colourful image during the spawning season as well, and they will eat almost anything offered to eat!
You could try small Perch (2-3"

and if they outgrow their acconmmodation at some point in the future you could always replace them to their 'home' and renew the cycle with another 'shoal' (as Holger suggests) from the wild.
I have kept small Perch in this way but they did take a long while to come to terms with the confined area of the tank (36x15x15) and the comings and goings of people, mostly hiding amongst the plants but they settled down eventually, eatring maggots and small worms.
I also once had a six inch Pike which was a great pet, feeding on worms and, latterly, small fish. But this outgrew its surroundings quite quickly and went back from whence it came...I never managed to ever obtain another little Pike, although (them being my favourite 'natural' fish) I'd dearly love to again...
John