The Free On-line Aquaculture Dictionary

Air Lift calculation
Maximum water flow from an airlift pump
Limitations of calculation (outwith these parameters the calculations will become less accurate):
  Pipe diameter 1.5 - 8cm
  Pipe length 60 - 300 cm
Q = ((0.758 x (%s)1.5 x ht0.33) + 0.01196) x d2.2
Where ;
Q = Water flow rate, litres per minute
ht = Total length of pipe (cm)
d = diameter of pipe (cm)
%s = Percent of pipe under water (measured from point of diffuser to discharge)
Air requirements for optimal water flow are typically 8-9% of the water volume. Above 10%, normal bubble flow ceases and the efficiency of the airlift drops rapidly