At the beginning, I would like to briefly explain some basics for the aeration of the GN-Jet lifter®.
The water column above the drive creates a counterpressure that the air must overcome in order to be able to exit the air hose into the aquarium at all. 1cm of water depth corresponds to approximately 1 millibar of back pressure. If the jet lift drive is located at a water depth of 30 cm, the diaphragm pump must apply more than 30 mbar in order to blow air into the drive at all.

The air volume indicated on the air pumps in litres/minute or per hour is only valid at the indicated water depth. As the water depth increases, the air volume decreases considerably. Good air pump manufacturers supply a characteristic curve showing this relationship.

Long 4/6mm air tubes act as a resistance. At the end of a long, thin tube, considerably less air arrives than comes out of the pump without an air tube. If several tanks are to be supplied, the air should be routed to the tanks with as thick a hose as possible, and the 4/6mm tube should be as short as possible. A ring supply of PVC pipes above the pools is the optimum, but is not always feasible for optical reasons.

All air pumps worthy of the name have an air filter in the intake duct. Of course, this must also be cleaned from time to time.

When operating several pools, please ensure that the air pressure spreads evenly in all supply lines (connected systems). If there are large differences in the depth of the air injection, the air will come out more strongly at the diffusers with a shallower depth. The deeper diffusers run worse or not at all. However, +/-5cm usually does not matter.

From now on, characteristic curves are also available for the GN-Airlifts® from which the air requirement and flow rate can be seen.
It took a lot of effort to create a measuring set-up in which the relationship between air pressure, air quantity and water quantity pumped can be measured repeatedly and over a long period of time. The biggest problem was to keep the water level constant in both tanks (the one being pumped from and the one being pumped into). An aquarist friend of mine (Robert R.) did this for me. Many thanks to Robert at this point.

Reinigung

GN Air lift drive 12mm

Tube diameter:
12 mm

Flow rate
130 L/h

Aquarium size:
60 litres*

Here it is clear that the maximum water volume of 135 litres/hour is already reached at 2 litres of air per minute. The measurements have shown that the air lifter already delivers the maximum with less air, but the low air volume could no longer be measured with this measuring set-up. More air displaces the water in the riser tube and the delivery rate decreases slightly. Since the riser tube is 15cm long, a pressure of 20mbar is completely sufficient.

GN Air lift drive 16mm

GN-Antrieb 16mm

Tube diameter:
16 mm

Flow rate
230 L/h

Aquarium size:
120 litres*

Here it is clear that the maximum water volume of 235 litres/hour is already reached at 2,8 litres of air per minute. The measurements have shown that the air lifter already delivers the maximum with less air, but the low air volume could no longer be measured with this measuring set-up. More air displaces the water in the riser tube and the delivery rate decreases slightly. Since the riser tube is 20cm long, a pressure of 25mbar is completely sufficient.

GN Air lift drive 20mm

GN-Antrieb 20mm

Tube diameter:
20 mm

Flow rate
700 L/h

Aquarium size:
350 litres*

Here it is clear that the maximum water volume of 700 litres/hour is already reached at 6 litres of air per minute. The measurements have shown that the air lifter already delivers the maximum with less air, but the low air volume could no longer be measured with this measuring set-up. More air displaces the water in the riser tube and the delivery rate decreases slightly. Since the riser tube is 25cm long, a pressure of 30mbar is completely sufficient.

GN Air lift drive 25mm

GN drive 25mm

Tube diameter:
25 mm

Flow rate
900 L/h

Aquarium size:
500 litres*

Here it is clear that the maximum water volume of 900 litres/hour is already reached at 10 litres of air per minute. The measurements have shown that the air lifter already delivers the maximum with less air, but the low air volume could no longer be measured with this measuring set-up. More air displaces the water in the riser tube and the delivery rate decreases slightly. Since the riser tube is 30cm long, a pressure of 35mbar is completely sufficient.

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