I finally got the time to put this together. I used the gravel vac end of my python and a Rio 90 powerhead. The python hose size was perfect fit for powerhead connectors. I had originally put a small foam at the bottom of the gravel vac but in my fiddling with it forgot to put it back. It was running already and I don't see any bubbles escaping so I didn't bother putting it back in. I do see my gold algae eater, cherry barb and a couple of otos go in there and try to swim upstream. One good thing about my placement of the diffuser is the bottom of the tube is right beside the intake of the canister filter, the CO2-rich water is sucked right in for spreading by the spray bar.