I've had quiet an extensive amount of experience w/ this skimmer before I upgraded to the "better" skimmers. It's was pretty finicky due to a few things.
- venturi air line was plugged
- inlet for air to venturi valve was plugged
- venturi valve/jet nozzle was plugged
It seemed as though most of the time fine particles/sand/calcium build-up would plug up these areas. I would adjust the skimmers while they're plugged (easily done even after cleaning) and once they get dislodged, would overflow the skimmer. This would happen so frequently after the first 6 months to a year. I upgraded to the Kent venturi nozzle which improved it slightly but over time got plugged too. I also upgraded to a Mag 7 which improved skimming but made the overflow frequency worse. It's actually the design of the nozzles/valves that is not very efficient at keeping these areas clear, I finally realized later when looking at better designed skimmers (needlewheel). I then decided to purchase a used Euroreef after a few years of frustration and never looked back. They're just better designed to keep stuff from getting clogged.
If you're stuck w/ it then I suggest every couple of weeks/months taking it apart and making sure all those areas are clear. If not, take a look at the better skimmers that don't pass all their water through a teeny tiny nozzle.
HTHs,
Minh
