I have the exact skimmer and havent heard good things about it, but it does a great job for my tank. I havent really had any problems.
Why is it overflowing all of the time? Do you have the valve too far open? One problem I had with mine is the little cannister that sits on top that connects with a small tube by the venturi input was not drilled on both side. That cannister with 2 nipples on top should allow air flow through both nipple.
When I drilled a hole in them it works like a charm. MFG defect.
Let me know what you figure out.
55 gal FOWLER with 2 Koralia 750 powerheads, Coralife 125g HOB protein skimmer, Fluval 406, 60 lbs of live rock.Butterfly, 2 Clows, 1 Cleaner Shrimp, Flame Angel, Purple Firefish, Snails, Crabs, Crown of thorns starfish