shade the portion of the coral that has skeleton exposed to discourage algae from growing on it.

Will try both suggestions, thanks!

Update: Alright, I've placed the donut under the overhang. The clowns seem confused since their little home has changed spots. I tried to implement more flow on exposed area/less light, but it's either one or the other.

Which one should I place emphasis on?

less light I would say...

less light. but you need to keep the affected area free of detritus. a turkey baster or something similar should do the trick.