I'm not opposed to your idea. However, I believe you need a 40B minimum to have any significant quantity of feeders. A 20g just isn't worth it. With a 40B, you could run 3 groups (3 females and one male) of mollies in 12"x18" knitting mesh basket. The fry fall through the mesh, and parents just keep breeding. This should give you enough home grown feeders to have a significant impact on your barracuda diet. Be warned though, once you prime the predatory instincts of a fish, it's there for good. Not a big deal if you're keeping pairs or solos. In a community, it primes all the other fish to eat fry. Just food for thought, no pun intended.