what would cause micro bubbles

[clevebill]

i have my return and my skimmer going into a filter sock but i still get micro bubbles into tank.my return is 3/4 pvc the only thing i could think is my elbow are not glued.ihave an elbow looking down into the tank then a short piece of pvc going into the water and an elbow directing flow.

 

[Kreeger1]

tiny holes in your hard glued plumbing, external pump? if so the fittings that connect to the pump could have a tiny air hole leak. To test for air hole leaks in plumbing look for salt creep on any plumbing joints, thats any elbows, t's connects to pumps, I had a bad ball valve once that let air bubbles in.

Do you have baffles in your sump?
Do you have really fine sand in your display?

Many many many possibilities and a headache to figure out.
Good luck

 

[Rhodophyta]

If the elbows aren't glued, you could be getting air in that way. Probably a good starting place. Good luck!