if you dont have good enough flow in the tank so that stuff can easily collect down in between the polyps and rot, there is your source fueling your algae.
besides clean water parameters and good flow, grab a handheld MJ 1200 once a week and blow out all nooks and crannies in your rocks and in between your polyps in order to get the stuff out of there so it wont rot and fuel your algae
If your water paramters are good, you dont need to disturb the polyps to get a handle on it....just keep blowing everything out regularly so it cant rot and you will slowly overcome the problem
Unmodded MJ are worthless as a means of flow in the tank....but they are perfect as a handheld cleaning tool. should only take a minute or two to celan the entire tank