Posted: Thu Jan 07, 2010 8:35 pm
Also make sure that there isn't any exposed place where air could be getting in the tube. I have an extension on my Aquaclear 500 tubing that isn't air tight. If the water drops below a certain level, the filter will behave just as you're describing.
After water changes, even with the filter primed (filled with water) I sometimes have to fiddle with the flow adjuster level to coax it to take up the water.
"You become responsible, forever, for what you have tamed." -Antoine de Saint Exupery-