I recall they liked medium to low flow. I started with 30, got like 400 in a year under 150w hqi 10000K, 6 inches under the waterline. Never fed them, sometimes they grabbed detritus, leftover food, but they relied on photosynthesis. To propagate them, i used pliers to cut a piece of the live rock with some polyps attached on it...then put them on other big rocks in many places in the tank and they grew quickly. It's a hardy coral. Looking at the pic, they look ok, they're not turning white or have cotton-like cover. Since when you got them ?