Anyone else have a Cascade canister filter....???

[PVChick12]

I have had my tank set up for about a week now, it was my friends that he had established for a year and a half. . . anyways, today i discovered the filter was running dry! After figuring out why....(the UV filter has to be above the cascade) I still had microbubbles which i thought I had solved, when in reality I had not solved it, merely stopped the pump altogether...so, any ideas? I know the bubbles are coming from the filter by the way, checked the pump/UV sterilizer already...I also have been told this means that somehow the filter is sucking in air, but I have no idea how to solve it, I heard to clean the filter, so I did, to no avail. . . other options? Thanks much!


pic of the filter btw: