I have been using Urchins.. About 25 of them to be Exact LOL... Those and not really feeding the fish all that much.. Maybe once per week... Other than that Its not really going away Fast... I have a mix from Fire Urchins, Long Spines and Pincushions as well as Lettuce Nudis, Snails and hermits.. I found that Mexican Zebra snails work good but they arent too cheap... I also put a piece of LR in my sump with no light and that seemed to kill it as well but I dont know how long that took... Its been down there for about a month or so... I think The Urchins did most of the work... Its definetly a PITA to remove... using a toothbrush, Stainless Steel brush and bristle brush didnt seem to do very much to it at all... I don't/won't use any sort of Po4 remover as that stuff has killed more of my corals than I can count...
James