The water pump is a Hailea hx-4500 and it has a capacity of 2500 litres per hour. Hailea makes liquid pumps that can operate with little water, making them ideal for use in hydroponics, ponds, tanks, and other applications. All of the low rate regulators on these handy small pumps are variable.
When it comes to NFT nutrient circulation, the HX series is your best bet. It works well as a filtering pump in aquatic environments, keeping algae growth to a minimum. The suction-padded feet on the bottom of the pump make it easy to attach it to smooth surfaces like the tank's glass or a plastic stand.
With the included mixing accessory for the HX-2500 and HX-4500 models, huge amounts of air can be mixed with the water while the pump is operating, significantly raising the concentration of Oxygen (O2) in the system.
These adaptable small pumps can operate in low-water settings and include completely adjustable flow rate regulators (not HX-2500). Oxygen intakes are also standard on the HX2500 and HX4500.
Pumps' precise flow rates are displayed in the options above. You may need a reducer for the following pumps if you don't already have the appropriate fittings:
HX-800 = a 13mm flexible pipe
HX1500 = 10mm, 13mm, or 13mm flexible pipe.
HX2500 = 13mm supply or flexible pipe
HX4500 = 19mm supply or flexible pipe