Bubble algea

[Ruth]

Well I am not sure. I have one bubble (that I can see) in my 230g so I am just going to leave it. I think the first thing to think about is why you are having an outbreak. I am pretty sure that mine is the result of a period of high nitrates that seems to be in control now that I have removed most of my sponges.
I think if I could I would remove the rock and try and wedge it out without breaking. If it broke - or even if it didn't - I would scrub the area it had been in with a toothbrush and then put it back in. If I couldn't get the rock out I would just try and remove without breaking but if it did break I don't think it is any big deal - unless like Beverly said it happens to be in a reproductive stage.