Originally Posted by eaglewonj
Do you have a protein skimmer on the system?
Protein skimmers dissolve a lot of gasses into the water as well as remove dissolved organics. I have seen similar bubbles from my canister filter and they stopped if I turned the skimmer off for awhile. I have Eheim biomedia in the canister....the supersurface area not only allows bacteria to grow all over but also gives a massive area for air bubbles to form from solution.
A little OT, but do you have an in-sump skimmer? I had problems with my skimmer putting bubbles into the tank as well. I fixed it by putting the pump right next to the skimmers exhaust tube. This way the pump sucks up any air bubbles that get spilled out of the skimmer so that they don't get sucked up into my main system pump. Since I did this, I have not had any bubbles get into my main tank.