Its valonia, (bubble algae), and can overrun your tank if your not careful. I have a single stock and a pair of stocks of neomeris annulata and it is a lot different. The bubble algae is almost see through and has fluid in it, neomeris is bright green, like flourescent green and has tiny little hairs around it, almost making it fuzzy. The bubble algae you have is long and thinner, which it the kind I have too. If you get some emerald crabs and don't feed the tank a lot they will get hungry and will eat the bubble algae. I will take a photo of the two tonight and try and post them to this thread.