i believe he is talking about air bubbles...
It is an algae issue - that is oxygen* forming from the near invisible algae that is multiplying on your rock.
Check your water parameters ..especially nitrates & phosphates, step up your water changes - percentage and frequency, change your GFO and carbon if you run them, and if you don't you might want to consider adding them.
If your lights are old, you might want to change your bulbs, but this usually happens due to water issues.
*...Jarred :hug:
I did know that, brain didn't engage...lol