Codium Geppiorum, Pacific...Oh, Johnny, you don't want this...it is very invasive and will commandeer the tank. I ID'd this and am currently trying to control it. I have started by removing as much as possible, performing a 30% H20 and introdicing some Emeralds, which are indifferent to anything they can cram into their mouths. One thing that eats it is Urchins of the Diadema (long spined) family (stetosum and one other, I forgot). If they were not so prone to knock things over, I would have on in there now.