a sump right now is cost prohibitive so I’m running my 120 gl reef with a canister filter. I would like to do a carbon and gfo reactor outside of the filter so I don’t need to change carbon bags out of the filter every two weeks. Honestly I never use carbon on my FW tanks. It’s messy, and looses its effectiveness so fast I never saw the point. But the more I’m researching reef the closer I’m coming to the conclusion that carbon is necessary. Is there such a thing as a stand alone carbon/gfo reactor ?