UNS CO2 Cylinder Pro

UNS CO2 Cylinder Pro | Shop CO2 Equipment Planted Tank - Glass Aqua

$84.99 USD

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Usually ships in 1-2 business days from our fulfillment center

IMPORTANT: Due to shipping regulations, CO2 cylinders are shipped empty and must be filled locally after delivery.

Please handle with care and follow proper setup guidelines. If you have any questions, feel free to contact our team at hello@glassaqua.com.

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

Ultum Nature Systems creates premium aquarium products designed by hobbyists, for hobbyists. Known for thoughtful design that first appeared in their line of rimless aquariums, they continue to move ground in the industry, with the health of your aquarium always at the forefront. Since the release, the brand has expanded into a variety of aquarium needs and everyday essentials that fuse form and function.

From best-selling substrates like Controsoil and Controsand to powerful filtration systems and nutrient-packed aquatic plant fertilizers for aquascapes at every stage, you're sure to find something you didn't know you needed. Jump further in and browse CO2 gear, various natural hardscape choices, then pick up some live aquatic plants and the tools you need to plant, maintain, and keep your tank looking its best. With a recent venture into the world of marine, UNS supports today's aquarium hobbyists every step of the way.

Inspired by nature and powered by the art of aquascaping, plan your next aquarium project with Ultum Nature Systems today.

Shop all UNS

Ultimate Planted Aquarium CO2 Guide

Adding CO2 to a planted tank might seem complicated at first—with all the gear and technical terms, it’s easy to feel overwhelmed. However, once you understand the basics, setting up a CO2 system for your planted tank is just as straightforward as setting up a filter or light. We’ll walk you through everything you need to know step-by-step.

Aquario Neo CO2 Diffuser Normal Large injecting micro CO2 bubbles

What is CO2 and why is it important in a planted aquarium?

Just as we need oxygen to survive, aquarium plants rely on carbon dioxide to thrive. CO2 is naturally produced by fish, humans, and other animals, providing plants with what they need. In a freshwater tank, fish naturally produce small amounts of CO2, which can give the impression that some aquatic plants don’t need it. In reality, all plants require it, just at different levels. This is why CO2 injection systems are strongly recommended—Popular beginner plants like Anubias, Bucephalandra, Java Fern and aquatic mosses are commonly labeled as “low-tech” because they can handle minimal levels. However, even hardy plants benefit greatly from added CO2 and will grow more quickly and vibrantly with it.

Aquascaper’s Notes: During photosynthesis (lights on), plants release oxygen, which helps keep the water well-oxygenated for livestock. As a result, most aquascapers skip traditional airstones or bubblers.

Easy beginner low light aquarium plant Java Fern Trident

Microsorum pteropus AKA Java Fern 'Trident' producing oxygen

Okay, so aquarium plants need CO2, but what does it really do?

For proper growth, aquatic plants require a balanced mix of light, nutrients and CO2. Think of it like a pie—each slice represents one of these elements. If any slice is too small, large or missing, the pie is incomplete and represents an imbalance aka ideal conditions for algae to take over. Injecting CO2 into a freshwater planted tank improves plant health, and stability. That’s why we recommend CO2 systems even in low-light or beginner-friendly tanks. It completes the pie, creates balance and reduces the risk of algae problems.

Common examples of planted aquarium imbalances:

Too much light, but not enough CO2 or nutrients
Too much nutrients, but not enough CO2

What equipment do I need to start injecting CO2?

The process is simple, once you understand must-have gear. Here are our four essentials every planted tank hobbyist should have.

1. CO2 Regulator

Controls overall output levels. Each regulator will have at least one gauge that will display the maximum output pressure. We typically set this anywhere between 25-40PSI (safe range) on the main valve and fine-tune the flow with the needle valve (the smaller one) to dial in levels being injected. Dual-gauge regulators show both working pressure and available gas reserves in the cylinder. Higher-end models may also include a solenoid. A solenoid lets you shut off CO2 manually or with a timer—usually synced with the lights, since aquarium plants will not require it when lights are off.

Shop UNS Mini CO2 Dual Stage Regulator CO2 - Glass Aqua

Almost all CO2 regulators will have a gauge that displays maximum output pressure

Shop UNS Pro CO2 Dual Stage Regulator CO2 - Glass Aqua

While other CO2 regulators will have dual gauges

Main pressure valve on an Ultum Nature Systems Mini CO2 Regulator

Needle Valve on an Ultum Nature Systems Mini CO2 Regulator

Ultum Nature Systems UNS Dual Gauge CO2 PRO Regulator for Planted Aquariums

CO2 Regulator solenoid example

2. Cylinders & Cartridges

These store CO2. How long do they last? This is one of the most common questions we get—and the honest answer is: it depends. Every aquarium is different. Factors like tank size, aquarium water chemistry, plant variety, plant density, and CO2 injection levels needed all impact how quickly a cylinder or cartridge is used up. Here are some guidelines:

Cartridges: Single use, compact and convenient. They are the perfect desktop solution for nano tanks between 1 - 8 gallons.
Paintball Cylinders: Budget-friendly option that is popular for convenience, size and ease of use. Most can be refilled at related hobby (paintball) stores. A great option for aquariums up to 20 gallons.
Standard CGA-320 Cylinders: Don’t let the name intimidate you! A CGA-320 is a North American standard that can be refilled at most welding, air-supply or local brewery shops. This is our top recommendation for all aquascapers who are invested in the planted tank hobby. This type of cylinder holds the most and will require less refills in between uses.

Planted Aquarium CO2 Injection Equipment

3. CO2 Diffuser

Delivers CO2 in the form of ultra-fine bubbles into the aquarium. Some aquarium airstones may look similar to CO2 Diffusers, but these aim to produce larger bubbles for surface agitation and gas exchange. The larger the bubbles, the more the aquarium will be oxygenated. CO2 needs to be easily dissolved in a planted aquarium, which means the smaller the bubbles, the better.

4. CO2-Proof Tubing

This is important. Normal airline tubing for aquariums cannot handle the higher pressure of CO2 systems. Specialized CO2 proof tubing is built to withstand pressurized CO2 and allows it to travel safely into an aquarium without leaks.

Ultum Nature Systems Pro CO2 Tubing | Planted Tank CO2 - Glass Aqua

Optional CO2 Equipment

1. Bubble Counter: Not required, but a helpful tool! Bubble counters provide a visual reference in the form of bubbles for how much CO2 is being injected into the tank.

2. Drop Checker: This small glass accessory hangs on the rim of the tank or suctioned to a glass panel inside the aquarium. They typically include a liquid solution that changes colors based on the amount of CO2 injected.

Yellow means too much CO2, blue indicates too little, and green means the levels are just right. It can take a few hours following installation or a water change to change colors!

Ultum Nature Systems Micro CO2 Bubble Counter | CO2 - Glass Aqua

Ultum Nature Systems UNS CO2 Drop Checker

If you’ve read this far, we hope you now have a better grasp on planted aquarium CO2 injection. If you’re still not sure and a full setup feels like too much, we recommend starting out with a simple CO2 Kit. It’s easy to use, beginner-friendly and great for many tanks! But if you’re ready to make that leap and full send into CO2 injection, check out our bundled CO2 Kits at discounted prices. As always, if you have any questions, our team is always happy to help!

Shop Planted Tank CO2 Kits

Overall rating: 4.875 / 5 from 16 reviews.

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Reviews

Uns CO2 cylinder pro 5lbs

"Finish on this cylinder is excellent. Really nice aesthetic touch so you don’t have to hide in a cabinet."

— Brentt L. (5/5)

New and as advertised

"Ordered two UNS CO2 cylinders from Glass Aqua (1 10# and one 5#) and both arrived in excellent condition with OEM manufacture dates within 1 year of purchase (to be filled/re-filled CO2 cylinders must be hydro-pressure tested every 5 years or so (~US$40), depending on your local jurisdiction, so this matters!). The white finish looks waaaay better than the usual dinged up aluminum cylinders do. . . if your cylinders are exposed, lol. Good stuff."

— Stephen J. (5/5)

Happy with CO2

"Picked up this 10g CO2 canister and dual pro regulator. Both look great, and are well made."

— Randy A. (5/5)

"The knob feels awesome. Very well made and looks awesome. Quite very reasonably priced for the quality. Only downside is that most of the places in my area exchange co2 cylinders rather than refill them. The one brewery supply store that does refills requires you to leave the bottle with them for a day. This means there’s a day or two of downtime unless you have a spare to swap in while you get the other filled."

— Jarim (5/5)

Beautiful 5lb Cylinder

"This UNS 5lb cylinder is a beautiful part of my CO2 system. It makes me look like a pro! My LFS filled it without issues and it works perfectly paired with the UNS dual stage regulator."

— Danielle C. (5/5)

Hello everyone

"I haven't used my cylinder yet but it looks clean and i am excited"

— Jeffrey J. (5/5)

Perfect and better price than

"Perfect and better price than my local store"

— Kevin O. (5/5)

Very nice looking cylinder with

"Very nice looking cylinder with good valve for a great price"

— Joel Z. (4/5)

Stunning

"First co2 system, this culi Fer not only works well but it looks very nice too, add a very nice touch to the whole set up"

— Luis O. (5/5)

"Had a couple of minor scufs but nothing to complain about. Works great and looks fancy. Thanks"

— Roger (5/5)

Q&A

Shipping
Orders are typically processed within 1-2 business days M-F. However, additional time may be required during peak seasons and federal holidays. For orders containing live plants, we exercise extra caution and assess factors such as travel distance and weather to ensure safe transit.

To avoid delays, please ensure all order information is accurate and complete. We cannot offer refunds and are not responsible for orders shipped to incorrect addresses due to errors in provided information. Once an order has been shipped, delivery times are determined by the carrier and are outside of our control. On average, shipments arrive within 2–5 business days, excluding weekends and holidays. For more information, please visit our FAQ page.

Returns
If you are not satisfied with your purchase, please contact us within 48 hours of delivery. Approved returns must be shipped back within 14 days of approval. Returned items must be unused, unopened, and in their original packaging. Specific return requirements, if applicable, will be listed on the product’s page. For more information, please visit our FAQ page.

Refunds
No worries, we’ll take care of everything as long as it fits the guidelines above.Most answers to general questions can be found on our FAQ page.

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