Hozelock Pond Biofilter for a 650 Gallon Pond Quality Pond Filter for all types of Water garden Fish Ponds, Can be partly buried Suitable For Ponds Up to 650 Gallons Size Comes with instructions Does not require Electricity to operate (Will need pond pump to operate) Max Gallonage is based on average conditions and fish load. For warmer USDA zones and high fish load increase gallonage of filter required.