Use the table below to select the correctly sized item. If you have any difficulties deciding which size is right for you, contact us by email or phone and we will be very happy to assist you. Although many factors including humidity, temperature, stocking density and surface area to pond volume ratio, can affect the Oxygen levels within a pond. We generally recommend a minimum air flowrate of: 100 Litres Per Hour (1.7 Litres Per Minute) / 1000 Litres (220 Gallons) of Pond Volume Or 450 Litres Per Hour (7.5 Litres Per minute) / 1000 Gallons (4500 Litres) of Pond Volume Air Pump | Litres per hour | Air Stones | Max Depth (m) | Max Pond Volume (Litres) | Watts | Single Outlet | 140 | 1 | 1.2 | 1000 | 4 | Twin Outlet | 320 | 2 | 1.4 | 2000 | 5 | Four Outlet | 640 | 4 | 1.6 | 4000 | 9 | PondOxy 1800 | 1800 | 6 | 2.2 | 10000* | 16 | PondOxy 2400 | 2400 | 10 | 2.8 | 15000* | 20 | PondOxy 3600 | 3600 | 20 | 3 | 22000* | 32 | * Volumes shown are for goldfish ponds, half them for Koi ponds. | |