Weatherproof Air Pump. Adding oxygen into a fishpond is very important for fish health, particularly in densely stocked ponds and in the summer months when oxygen levels decline. Air pumps can also be used to circulate water and help prevent the pond from freezing in winter. Specifications Max output: 640lph Air Stone max depth: 1.2m Output at 1m: 450lph Max pressure: 0.014MPa Air outlets: 4 Air tube length: 1 x 10m Air tube diameter: 4mm Air Stones: 4 Air Stone size: Ø3cm x 3cm Pump rating: 8w Cable length: 3m Comes with a 2 year manufacturers guarantee.