PondMax Pre Filter Sponge for Pond Pumps [100 x 100 x 150mm] Pump Pre-filter Sponges attached to your pump and greatly increase filtration. A pre-filter sponge can be used for filtration on pumps in ponds, aquariums, or aquaponics systems. Ideal for both pond and fountain pumps Increases efficiency of pump Provides mechanical and biological filtration for your pond Leaves you more time between cleaning the pump sponge due to large surface area The sponge is black and has fine spacing to catch small particles and accommodate good bacteria. In the centre of the sponge there is a poly pipe which attaches firmly to the pump inlet. How To Fit A Pre-Filter Sponge To Your Pump: Remove the existing inlet / sponge cover and the sponge from the pump as if you are going to clean your pump impellor Check the thread diameter in front of the impeller If the diameter is 1/2, 3/4 or 1 inch the Pondmax Pre-filter Sponge will screw straight in Sponge Dimensions And Pump Suitability: 10 x 10 x 15cm Suits 500 - 2000L/hr pond pumps 10 x 10 x 30cm Suits 2500 - 4000L/hr pond pumps 12 x 12 x 30cm Suits 2500 - 6000L/hr pond pumps Thread Sizes which suit: 1/2 Inch / 15mm BSP 3/4 Inch / 20mm BSP 1 Inch / 25mm BSP