Well, let's see...the flow over the biowheels is fine, although I keep it kinda slow. Should I speed this up a bit? I think the inlet tube is the same thing as the suction tube you mentioned, right? If so, yah, the tube is in tight and it's way below the water line, so I don't think any air is getting in there. My water line fluctuates ( evaporation ) but I get lots of bubbles no matter where it's at...Hmmm...any other ideas? <img src="graemlins//confused.gif" border="0" alt="[confused]" /> <img src="graemlins//confused.gif" border="0" alt="[confused]" />