I have always dreamed of having a community tank that was as close to natural as possible. Were fish feed of each other, plants, and invertabrids with little feeding. I have heard of some people having tanks like this. What stock would you use?
If you only have one predatory fish that shouldn't happen will it.To create a self sufficient system is possible. Heck My Mbuna tank is pretty much there at 160g, heavy lighting creates lots of algea, low snail population, Mbuna feed of the rocks, i have a couple haps/vics and between them and the competition between various Mbuna species it keeps the fry numbers in check.
But even if it's 300-500g you would only be able to accomidate a few Small predatory species in with MANY community type fish. You can introduce blackworms, snails inverts etc too help feed the lower end of the food chain but also to help maintain substrate and take care of plant debris. good lighting will be key to success because because it'll be plant growth and algea's at the bottom of the food chain as well as creating breeding areas.
I think anything mediem-large and predetory will wipe out the others though unless it's a large pond setting. But could get away with smaller bichirs, rope fish, ceno's, leaf fish , small knives etc. Make sure the pred ratio is very low to maintain a balance otherwise it'll quickly ruin everything, remember that enclosed in a tank the pred's have a huge advantage !