Hi, the best way to treat for ich is hyposalinity, IMO. But I also starve the tanks to eradicate the lifecycle which means pullling all the fish to do so. It's can be a hassle, but I've gone through the few weeks it takes with garbage cans gurgling away with fish in them while the ich lifecycle is decimated because there are no hosts in the main tank. More folks can help you with that, and perhaps someone can link you the procedure.
What to feed? Omega One Veggie Flakes work well, as does Formula II frozen. We feed ours both - and he seems to be just fine. HTH.