They are very slow to start skimming- mine ran for a full 6 weeks before it started skimming. They are sensitive to certain things; mine goes flat whenever the southdown gets stirred up. My 6 week problem (I think) was due to the fact that I had a thin coat of southdown dust covering everything in my new setup, and as it aged algal and bacterial action continually lifted bits of sand into the water. I added a bunch of snails to the sump and when they cleared everything of it started skimming soon after...
Anyway, my sump is deep (basement stock tank) so I built a 2x4 stand for the skimmer that holds the whole thing slightly above water level. I keep the water level right at the base of the tower. I was using a mag7, but since it had to pump up a couple of feet I switched to a mag9. This produces a bit too much foam, so I have dialed back the air intake slightly. I might try the mag7 again.
All that said, it runs very steadily and nicely- requires no ongoing adjustment. One thing I noticed early on- I have an L tube dumping the water back into the sump. If it terminates below the water level it sets up a siphon and lowers the level in the skimmer too much. I terminate above the water level now and the water level can be controlled with the exit ball valve no problem.
I take off the removable part of the tower every 4-5 days and clean it, I also wipe the inside of the fixed tower with a paper towel.
