Green Bubble

Ive had a little bit of green bubble algae in my tank for a long t ime now. Pretty sure it came in on a frag and I have only seen it pop up a few bubbles every couple months which I manually remove without bursting very easily.

Well today I went to go kill an aiptasia with aiptasia x and after I siphoned the gunk out of the hole I saw what looked like a little pillow. Reached down and sure enough there was bubble algae INSIDE the rock, I thought it would need like to grow why would it grow in the darkness and not in the open? Seems to be slow growing but I am afraid of what the future holds anything I should do?

 

emerald crabs eat it up! just dont pop the bubbles!