This tank is actually pretty low maintence. The only filter system on it is a Coralife 220 super skimmer and 2 powerheads. But then again I only have 2 fish in it, so the live rock filters most of it.
The Coralife skimmer is rated for up to 220 gallons, so a 40 gallon tank is easy work for it. I've been happy with it so far on my tank, and even one the 100 gallon when it was on there. But not sure if it'll be able to keep up on the 180 really. If I had more money I'd get a ASM G3 or G4 skimmer (about $375-500). But as far as a hang on style Coralife's skimmers seem fine, they bubble alot at first and take a while to break in.