I have had this problem for sometime. I has been growing in my sump at an alarming rate and coats the sump sides and pumps mainly. I have the refug light on for 10 hours at night opposite the tank lights. I do find some of this algae growing at the top of the back of the aquarium.

I tried to use Antired but not did not help. I use phosguard and change it out regularly. I have an emerald crab in the sump but he does not touch it.

Any other ideas or remedies?