The BT700 filter comes with a range of fittings to enable it to be used with a jet , spray bar or even a venturi outlet to give added airation. Suitable for aquariums up to 250 litres. Or aquariums up to 48" long. Can be used with tropical or coldwater fish. Inside the filter there are handy cartridges which contains carbon - this will purify the water and make it crystal clear, the carbon can be replaced or the cartridge can simply be swapped, this is best done every month. The sponge filter will trap dirt as well as house the beneficial bacteria to break down any fish waste. Spares are readily available.