getting fine bubbles on rocks any ideas why?

[reefsahoy]

i seem to be getting fine bubbles over rocks and sometimes on my corals, anyone have any idea why? i'm not blowing any bubbles in the tank and my water measures
0 nitrate
0 silicates
0 phosphates
8.5 dkh alk
8.3 ph
1400 mg
400 ca

 

[jessp]

is overflow putting bubbles in the sump that your baffles can't eliminate?

how is your sump set-up?

 

[reefsahoy]

no bubbles being pumped into tank. i just added some crabs to see if it's the begining of algae or what. i had completed the interceptor treatment for red bugs a month or so ago which killed all my crabs and that's why i'm thinking a lack of crabs.