Hozelock Pond Air Pump 1500. Hozelock Pond Air Pump 320. Adding oxygen into a fishpond is very important for fish health, particularly in denseley stocked ponds and in summer months when oxygen levels decline. The smallest model in the range delivers 320 litres per hour with a maximum operating depth of 1.2m and the largets model delivers 4500 litres per hour with an operating depth of 3m.