I am by no means a pro as you know, but what I did to prevent this in my sump is to hang a small piece of filter floss over the baffle between the skimmer and the return for a while. Once I got more a of a bioload, the problem seeto remedy itself. I also have the foam piece on the skimmer as high as it will go. This is just what I did when encountering the same issue with a cheaper 75 gallon eshopp skimmer.