from what i can see from the pic, I think the problem lies with the pump and the skimmer being put too closely together. (if that is a skimmer I see in the pic) cant really tell your setup from the pic.
If its a skimmer and if your skimmer allows, try directing the skimmer's water exit upwards so that the water comes out from the top of your sump and the bubbles dissipate from the top. or let the skimmer water land on a pieace of filter wool. that should reduce the bubble