Everyone has their favorites and they all really work about the same for the size you pick. So I want something reliable and easy to maintain and use. I'm a fan of the Tunze 9410 DC. It has a break in period of a week or so. There's no tuning required really and it supports a fairly wide sump level 5.5-9.5. Says up to 317 gallon but that's usually optimistic or light load - 120 will be fine. The DC pump is easy to adjust for the skim you'd like. Very easy cup removal and fairly easy to clean. It's older design which turns some people off. No swoopy curves, no jet nozzles of bubbles. It's German design for functionality, Tunze name and simply works. Slightly pricey (less so now a days though) but it'll last years.