I think the cheapest thing to do would be to buy a worm bin from your local farm supply company or whatever and just feed them the worms. I feed my fish the redworms and he loves em, but i still get the goldfish as a treat everyonce in a while, i think he has fun chasing them down! The bin is like 40 bucks, but every so often the worms regenerate and you are left with twice as many worms, plus you get some gardening compost and worms for fishing for panfish if you enjoy that at all.

Joel