High performance and optimal energy efficiency go hand in hand with this eheim professionel 4 250 external filter as well as being extremely quiet the filter also includes xtender technology which allows you to counteract blocked filter media and low water flow simply use the turning button to redirect the flow this innovation means that when the eheim professonel 4 250 gets dirty you dont need to clean it straightaway the xtender technology gives you a couple of days extra before you