You needs to get yourself a new custom sump with baffles to cut down the micro bubbles. In the mean time, you can try to put your pump inside a 5 gallons (or 2.5 gallons) aquarium. Rotate your skimmer so that the output is farther away from your pump. But I don't think that will help much w/ your current sump setup. Euro-reef tend to go crazy if you feed some frozen foods or add additives to the tank. Have you cleaned your skimmer yet since you got it? After that you can try to cut down the micro bubbles by adjusting it accordingly.

Some peoples build PVC pipe to reroute the skimmer's return under the water level and throw away the sponge filter.