I went back and looked at pics on a larger screen. I see what may be derbesia which is similar to bryopsis mixed in. Yes, those will keep coming back unless you properly remove it. Removal is best accomplished by taking the rock out of tank and placing in a container of tank water. Then you will want to pull as much as you can by hand and discard. With a dental pick or small crochet needle, pull the roots off the rock. YOU MUST GET EVERY ROOT OR IT WILL SIMPLY RETURN !!
After you are done return rock to tank and reduce white light intensity and even hours of white light and add the following cleaners which will help with control. These guys will consume bryopsis but not as fast as bryopsis can grow - They will never keep up.
Pin cushion urchin, Chiton snails, pitho crabs, and larger astrea snails
This procedure is not as bad or time consuming as it seems. Assure phosphate levels do not become elevated which helps feed this algae
harbor Freight: