I moved my longspine urchin from my fuge to my main tank cause he ate a crapload of caulerpa and cheato in like 4-6 hours. He was draining any sort of macro any time he ever went near it. I've got a few urchins, have had several, and a few of them at a time seem to keep algae down fairly well
Maybe thats an option?
Cheers,
Chris