I just bought a tunze 9005 skimmer today and it's not working properly. The skimmer produces foam but it doesn't rise to the cup, kinda just stays in the tube. I've adjust the screw/valve but to no avail. Also I've followed the troubleshooting section in the guide (move the skimmer to an area of less current, make sure the water is on par with the water line on the skimmer) and still the foam ceases to rise. Any help would be greatly appreciated.