The UNS CO2 Pro Cylinder is a long-term CO2 source for planted aquariums, offering larger refillable capacity for hobbyists who want extended runtime and fewer refill trips. Available in 2.5LB, 5LB, 10LB, and 20LB sizes, these cylinders are designed for use with standard CGA-320 CO2 regulators and are ideal for medium to large planted aquariums, high-tech aquascapes, and multi-tank CO2 systems.

Most hobbyists can refill their cylinder locally through welding supply shops, gas suppliers, beverage distributors, or brewery supply stores.

Best For
- Medium to large planted aquariums
- Long-term pressurized CO2 systems
- Hobbyists looking to minimize refill trips
- Hobbyists using standard CGA-320 regulators (UNS Pro Dual Stage and Mini Regulator)
- Multiple aquarium systems using a single CO2 cylinder

Why Choose a Refillable CO2 Cylinder?

Longest Runtime Between Refills: Larger CO2 reserves mean fewer refill trips and less interruption to your planted aquarium system.
Ideal for the UNS Pro Regulator: Designed to pair with the UNS Pro CO2 Dual Stage Regulator for a stable, long-term CO2 system.

Available in Multiple Sizes: Choose from 2.5LB, 5LB, 10LB, or 20LB cylinders depending on cabinet space, aquarium size, and CO2 demand.

Refillable CO2 cylinders are the best long-term option for hobbyists running dedicated pressurized CO2 systems. They require more space than disposable cartridges or paintball cylinders, but offer longer runtime and are often more economical over time.

Product Compatibility
- UNS Pro CO2 Dual Stage Regulator (compatible out of box)
- UNS Mini CO2 Dual Stage Regulator (adapter included and pre-installed)
- Standard CGA-320 CO2 regulators

Important Information: CO2 cylinders must be filled by a qualified refill station before use. Always transport, store, and operate cylinders securely in an upright position. Follow all local regulations regarding compressed gas cylinders.

Hydrostatic Testing: CO2 cylinders must be hydrotested every 5 years in accordance with U.S. Department of Transportation (DOT) regulations. This inspection helps ensure the cylinder remains safe for continued use and refilling.

Setup & Filling Information
Before use, make sure your CO2 cylinder has been properly filled and that the main valve is fully closed. Install a compatible CO2 regulator and ensure all regulator valves and manifold valves are closed before opening the cylinder valve. Once everything is securely connected, open the cylinder valve fully and adjust working pressure according to your regulator and aquarium needs.

Model Specifications

2.5LB CO2 Pro Cylinder
Volume: 2.5LB / 1.68L
Height: 11.02” (280mm) without valve
Weight: 3.86LB (1.75KG)
Working Pressure: 139 BAR / 2015 PSI
Test Pressure: 232 BAR / 3364 PSI
Material: DOT3AL Certified

5LB CO2 Pro Cylinder
Volume: 5LB / 3.35L
Height: 14.53” (369mm) without valve
Weight: 6.61LB (3KG)
Working Pressure: 124 BAR / 1800 PSI
Test Pressure: 207 BAR / 3000 PSI
Material: DOT3AL Certified

10LB CO2 Pro Cylinder
Volume: 10LB / 6.7L
Height: 16.93” (430mm) without valve
Weight: 13.22LB (6KG)
Working Pressure: 124 BAR / 1800 PSI
Test Pressure: 207 BAR / 3000 PSI
Material: DOT3AL Certified

20LB CO2 Pro Cylinder
Volume: 20LB / 13.4L
Height: 23.62” (600mm) without valve
Weight: 23.80LB (10.8KG)
Working Pressure: 124 BAR / 1800 PSI
Test Pressure: 207 BAR / 3000 PSI
Material: DOT3AL Certified

What’s Included
- UNS CO2 Pro Cylinder