Try putting a sponge on the Skimmer output if you can it will reduce the number of bubbles that escape. Once the skimmer starts to produce a thicker foam, the micros bubbles should start to go away. Another good idea is to have the output of the skimmer as far away from the return as you can so that the bubblws will surface in the sump and not get pushed up to the tank. What the h#$% add a baffle between the skimmer and return and it might block them there as well. There are a lot of options, it all depends on your setup and ability to build. Good luck.