Before adding any stuff, maybe tell us how many (and what type of) snails and crabs do you have? A cleanup crew is usually the best method of taking care of the various algae cycles in a new tank.
That's a 90, right? A couple dozen snails (Astreas are good) and 6-10 crabs (Scarlet Reef hermits are good) will get that back in shape, and help you stay ahead of the next wave of scummy gunk.
