There are obviosly some bubbles floating around in the water, I would look for the source of bubbles and try to fix that, and use a turkey baster to blow the accumulated bubbles out from under the rock.
I get bubbles under the LR sometimes because my skimmer will introduce tiny bubbles into the water and it will accumulate under the rocks. To combat this i have the water from the skimmer's overflow, running down through a flolded piece of 50micron filter pad. This does not get rid of all the bubbles, but it takes care of most of them. My skimmer just sucks.