Needle Valves are used for precision control of the flow of CO2 gas, which is not possible by use of the regulator alone. The bubbles should be fine tuned so that they are VERY SMALL and rise slowly and lazily to the top of tank, but almost become absorbed about 1-2 inches before reaching the surface. This way maximum use of the CO2 gas is achieved.
This needle valve is manufactured to high standards. The unit is a miniature precision needle valve, for sensitive and repeatable control of gases such as CO2. The Needle Valve can give precise control of CO2 gas when installed as directed, thus enabling the optimum use of CO2 gas in the aquarium.
Easy to use, your CO2 tubing simply pushes into either end of the Needle Valve. The small dial on the top simply increases or decreases the amount of flow you require when you turn it. This needle valve only accepts CO2 tubing of 4mm internal and 6mm (which is the same size tubing of all our CO2 tubing).
Tip: if you are planning on using one regulator to feed off to more than one diffuser, you will need one needle valve for each line of CO2. Failing to do this means gas will always find the route of least resistance and your flow rate will not be consistent. So to confirm, assuming you want 2 x diffusers in your tank, your set up would be:
1 x regulator, 1 x Y splitter, 2 x needle valves, 2 x non return valves, 2 x bubble counters and 2 x diffusers.