Originally Posted by joy13
One of my HOB
filters was doing the same thing, I didn't realize it right away but the filter wasn't resting against the back of the tank. I put a small box between the filter and the tank to level it out and it worked.
I was just about to mention this.
There is a little notch or could have been a notch on the carriage box. This can force your filter forward a bit. You can adjust this so that you filter is perfectly parallel to your tank as it hangs.
As for the space I mentioned, there should only be a small space left at the base for the water to flow roughly the measure of 2-3 quarters stacked on each other.