Modding a Bubble Magus Curve 5?

[fishwater]

I have a bubble magus curve 5 skimmer. It works ok, but I feel like it should be pulling more. It's in a 40 breeder with 25 gallon sump with 4 fish. Are there any mods you can do to increase production?

 

[Hentz]

Following.

Your tank could be too clean or something might be in the airline or something.

I have two BM5's. The one on my Reefer 170 isn't skimming for crap, although I run ZEOvit so my nutrients may be too low. However the amount I feed, I have a hard time believing that. I have ran the Airline tube outside of my enclosed stand. It has increased the pH fluctuation and it has had some noticeable difference in skim, barely.
My frag tank is skimming like crazy with a fluctuating water level in the sump, haven't setup my ATO yet.