I use a finnex PX-360 Hang on canister .. three of them in total,
all hanging on 4 gal finnex rimless tanks.
I've had great luck with them so far, one is pushing 3 years old now.
I Skip the expensive floss pads and just use bulk floss.
work great, last long, and quiet
Link:
http://www.amazon.com/PX-360-All-one.../dp/B002VFF8U4