Model 70 offers both forward and reverse water flow. The use of reverse flow through an under gravel system promotes bacterial growth from the bottom up, increasing biological filtration capacity. The injection of water containing oxygen beneath the gravel bed helps to support superior conditions for beneficial nitrifying bacteria. Substrate maintenance is facilitated by debris being located near the surface for easy removal. Dependable Service Supports efficient filtration Flow Control Reverse Flow Option Aquarium rim attachment fits easily to all standard aquarium rims Solid, durable, compact pump construction Epoxy sealed motor Hermetically isolated from water?fully submersible Water movement switch controls reverse and forward flow Fully variable output control suction cup bracket allows custom and deep installations Noise suppressor air filter quietly removes airborne contaminants before they can pollute Free floating impeller "Venturi" aeration device increases surface agitation and gas exchange efficiency