Gravity return pond filters and pump

What is a gravity return pond filter and pump

Gravity return pond filters consist of are a filter box which sits outside of the pond and are fed by a pump within the pond. Water is pumped up from the pond into the filter where it then simply passes through the filter media and returns to the pond under gravity. The only requirement for this type of pond filter is that the outlet is higher then the return point in to your pond. The advantage of this type of pond filter is that it can be scaled to a much bigger size than the pressurised filters so is ideal for koi or heavily stocked ponds due to the high waste produced from these type of ponds.