Hey Ron,
There are so many different algae species from around the World that come in on
LR, LS and even in minute fragments in fish water from the
LFS. It really amazes me. I can't ID your algae but, the best course to follow with problem algae is find the source of nutrient it's using, religiously pluck it from the tank, faithfully do your water changes and find a desirable algae such as, chaetomorpha (sp), Gracelaria red or green and others to grow in your
sump/refugium. They will compete for nutrients that the nuisance algae is using. Eventually, following a rigorous campaign against the foe, the good algae in your
sump/refugium will eventually win and the nuisance algae will be gone or at least reduced to a tolerable level.
What are your water parameters? Especially
Nitrate and
Phosphate?
Dick