For both tangs and angels, live rock is best. It provides them with a in tank buffet to graze on a supplement nutrition. With that many fish, I likely wouldn't add anything. Might be small fish now, but they won't stay that way. In my 120, I have 1 damsel, 1 bicolor angel, and 1 yellow tang. That's it for fish. With 3 tangs, you're going to be pretty crowded once they hit maturity and start staking out territory.