heres some info on byprosis
This probably is Bryopsis . It is a nuisance alga that is difficult to remove and will not be eaten by most common herbivores. It is common to have blooms of Bryopsis during the early months of a tank's life, however, in time it recedes. Some aquarists have reported that it may disappear altogether given that tank water quality is maintained. But most importantly, the aquarist must take proactive steps, such as manual removal, to limit the growth of Bryopsis (especially in a mature tank). It is possible that nutrients are taken up by the holdfast of this algae so blowing detritus from the rock it is on may help to keep it under control. Tridachia crispa, the Sea Lettuce Slug, is a hardy specialist predator of Bryopsis and is available from aquaculturing facilities such as Inland Aquatics. However,it is a true specialist and will perish after all the alga has been consumed unless an effort is made to culture or otherwise provide the alga for its comsumption. John Rice has a nice page devoted to his battle with bryopsis here.
byprosis page
blasting it with a turkey baster to clean up the area around it before doing water changes helped also kept pulling it out by hand. that worked in our tank
