I use an eheim 2217 on my 50gal reef. I actually use it as a glorified pump. It only contains about 10lbs of base rock. I do not use any of the canister filter media as this would create nitrates. I only use the canister because it was leftover from a FW set up and I do not have a sump. It also comes in handy when you want to use chemicals(carbon, phosphate pad).
Brian