fastest way to speed up coroline growth, is to add 5 to 10 lbs of good live rock. and also, get some small pieces and scrap them with a stiff brush or knife, put the scrappings in your tank. the spoors will spread to your dead rock. I used a lot of base rock, and now about 4 months later i am already getting good growth . make sure your calcium levels are good, and plenty of light. It will come back, just takes time.