If you want to keep a lion dont get a trigger, those flowing fins can get nipped fast by many triggers, may be able to get away with one of the Xanthicthys triggers (Bluejaw, Sargasum etc) but a picasso / clown would be bad.

If no triggers then you could get a few urchins, also a few of those golfball sized turbos would probably be ok, would be worth trying - if you don't have corals to worrk about them knocking over they are awesome for algae control (one of mine helped me frag my red montipora digitata today!)