Yellowish spots on montipora
 

Any idea on what would cause these yellowish spots? My monti used to look great, bright color, full polyp extension. I had to go on a reduced lighting schedule to get rid of some hair algea issues and it still hasn't recovered.

looks like die off and its quite pale, did you by chance use anything to assist with your algae control? any additives or "special" remedies?

Nothing special just limited the lighting to 4 hours a day for a little over a week, ramped up the GFO and carbon to get rid of organics and PO4. Scrubbed all the rock and did a few water changes. All the corals in the tank got pretty stressed during that time frame with the lights out, I noticed some die off on the others as well.

Just wanted to make sure it wasn't a pest or anything else. So it could just be die off from the lighting change I suppose. Hopefully it will may a comeback with the lights back to normal schedule.

Probably related to the increase in gfo or carbon. I know the only time I had rtn in my tank was when I turned on my gfo reactor. Never again.