What is this?

[Knoxjoelee]

they look like bubbles I have no idea what they are? Look in the middle of pic.

 

[dan987]

Bubble algae.
I see an emerald crab in your future.

 

[SeahorseKeeper]

Bubble algae.
I see an emerald crab in your future.

+1. If you pop them, they will release spores and reproduce like crazy in your tank.

 

[LetItReef]

+1 Do not pop inside the tank. Found one in a frag I bought. I scraped it off using a sharp razor blade, dipped it and put back the frag in the tank, no issues.