Cascade has just been hell from day one Even getting it primed the first time. I used other canisters on tanks years ago and had this problem. See why Pen-Plex Cascade is so cheap.
Yeah, I'm curious about this priming issue as well. Granted I haven't owned it long, but I've got a Penn-Plax Cascade 1500 running on a floor level 55gal and it primes and takes off with no trouble. I use the coarse sponge in all 5 baskets. I've owned a bunch of different make/model canisters at this point and the Penn-Plax are awesome for the price. My 1500 was like $135+ tax shipped. It moves and filters a lot of volume for the dollar. The plastics definitely feel better than something like a Sunsun. Here's a pic of my Cascade 1500 next to my 8yr/old Marineland C360 that's used for the top tank on this double stand.