Distributing CO2 to Multiple Aquariums with a Splitter

If you have several planted aquariums, it is entirely possible to supply CO2 to each from a single source using a CO2 splitter. This reduces costs, centralizes the setup, and improves efficiency. Here is a complete guide to properly install, connect, and adjust your system.

What is a CO2 Splitter?

A CO2 splitter is a metal or brass fitting that allows you to divide the output from the regulator into several CO2 lines. Each output can be independently adjusted thanks to a built-in fine valve.

1 input (from the regulator)
2 to 6 adjustable outputs (depending on model)
Screw-on installation with standard threading (often G1/8 or W21.8)

Required Equipment

A CO2 regulator with compatible threading
A CO2 splitter (2 or 3 ways depending on the number of tanks)
High-pressure CO2 tubing
Check valves for each line
A CO2 diffuser per aquarium
(Optional) male-male or female-female connectors to adapt positioning

Installation Steps for a CO2 Splitter

Attach the splitter to the output of the regulator (check thread compatibility).
Optionally add a fitting to properly orient the pressure gauges.
Connect a CO2 tube to each splitter output.
Insert a check valve on each line, followed by a CO2 diffuser.
Check each connection for leaks with soapy water.
Adjust the flow individually according to the volume of each aquarium.

Tips and Adjustments

Recommended flow: about 10 bubbles/min for 100L.
Place each diffuser opposite the filter outlet to maximize dissolution.
Use a timer to cut off CO2 at night (via a solenoid valve upstream of the regulator).
Do not exceed 3 to 4 outputs to avoid general pressure drop.
Regularly test the pH and KH of each tank (some may drift differently).

Advantages of a Multi-Aquarium System

One CO2 bottle or extinguisher for multiple tanks
Centralized installation = space-saving
Long-term savings
Better overall system control

Conclusion

The CO2 splitter is a practical and economical solution for enthusiasts with multiple planted aquariums. Properly installed, it allows stable and adjustable diffusion in each tank, avoiding multiple regulators and cylinders. Test, adjust, and enjoy an optimized system.