I presently have a Predator skimmer (forget the model, but it is a fairly large external thingy), but it really is too small for my system and not terribly efficient. New LFS has talked me into a rather large external EuroReef skimmer which he promises me he will install. A bit pricey, those big external EuroReef skimmers are. Made for a 300 gallon system. I have about 350 or so gallons. Hope it will do the job. I'm told they will handle far more than the stated # of gallons.
Started with a less than ideal Prizm skimmer. Inefficient, loud, and tempramental. It's shoved in the back of my fish closet somewhere...