The EHEIM professional 4+ - Eheim' s best external filter but now with an integrated emergency button. Adopting the many advantages of the professional 3 series powerful performance optimal energy efficiency quiet operation priming aid safety hose adapter but also improved technology by incorporating the new Extender button. In the event the output is reduced due to the fine filter media blocking the button can be adjusted to redirect the flow. The biological filtration is maintained and the service interval can be extended by a few days. Advantages of the EHEIM professional 4+ filter Premium class external filters with all the advantages of the professional 3 series. For aquariums 120lt to 250ltAdditional control function (Extender) to counteract blocked filter media and extend intervals between cleaning. Square canister for high stability and large filter volume High flow capacity with low energy consumption. Adjustable pump output. High performance ceramic axle guarantees quiet running and durability. Integrated self priming aid to initially prime the filter. Safety hose adapter can only be removed when the valves are closed. Top prefilter effectively traps large dirt particles and allows for longer. Service intervals. Simple to remove and easy to clean. Individual filter baskets with "Easy Clean grid. Fully equipped with original EHEIM filter media and installation accessories.