I had the same problem with my skimmer. I took a small tuppeware container with holes drilled in the bottom, put a carbon pad and filter floss in it, and sent the outflow of the skimmer through this. So instead of having the skimmer outflow go directly into the sump it goes through the filter floss and the bubbles get trapped in the floss material. It worked great for me. No bubbles at all after I tried this. I used a 3" piece of PVC pipe to support the container above the sump water level.