The M25 gravity return FB unit will cater for heavy stocked ponds up to 2,500 gallons (11,250 litres), and is best served from a high pressure pump offering around 470gph (like Blagdons Amphibious P2000) - with final operational flow rates of around 250gph. nThis unit is approx 600mm high (24") with a 110mm (4") diameter core containing 3kg of silica sand, together with standard 38mm (1.5") inlet pipe manifold including a Cloverleaf Side Valve on the inlet side, together with a non return valve. nOutlet/gravity return is for 50mm (standard 2") rigid pipework. nThe M25 will support up to 50kg (110lb) of fish load.n