Yesterday I bought a Maxijet 600, and a Cascade biosponge, which is big enough to make two sponges for the powerhead. I cut small pieces to plug the hole in the end - the Cascade sponge has a hole down the middle. I poked the CO2 line thru the sponge plug and into the plastic grid thingee that is made for sponge filters and comes with the Maxijet. Today I replaced my Fluval 104 and the minijet pump I was using. So far it works pretty good, but I wonder if the CO2 bubbles are actually sucked back down into the impeller. I'll keep watching it before I decide it is working well. Very nice idea though - no more spraybar, no more filter inlet tube, no more blockage of filter inlet or minijet inlet. And, I have to look hard to see it in the tank.