[Fortuna Wolf]

I've found that with impeller dispersers simply putting the hose into the intake will result in "bubble explosions," the loud and scattered bubbling that some of you are seeing.
What I did was just below the green flow adjuster I drilled a 7/16" hole (though really, .2" would have been ideal), and then put one of those white, long, and skinny airstones in it with the barb sticking out of the hole. I then connected the airline to the barb. This creates a steady stream of small bubbles that then get broken up silently and into even smaller bubbles by the impeller. No sponge catch necessary, though you can still add that if you want all the co2 to dissolve.