I had a rock with yellow polyps on. I fed home-brew Phyto and bought Zooplankton. The rock also had some hitchhiker anthea (sp?) that went crazy, as have all the other corals in my tank. The yellows though simply slowly disappeared, nothing I did seemed to make any diference.
The antheas, that's another story - growing like a weed - my lawnmower blenny just LOVES sleeping in the long tentacles!
Everyone said the yellows would reproduce like a weed, couldn't keep them alive in my (otherwise extremely healthy) tank