If you're talking about the bubbles then I believe it is grape caulerpa or bubble algae. Harmless until it starts to multiply and multiply.Any idea what these are and are they bad?
Lol it took me weeks to spell it right.green grape caupulara , I know spelled it wrong lol herbivores love munching on it . it can take over if not maintained here's some literature about its + and - about it and it's counter parts http://marineplantbook.com/marinebookpage15.htm