How to Set Up an Aquarium CO2 System the Easy Way


Beginners are typically advised to start with straightforward, slowly growing plants in planted tanks that just need little lighting and all-in-one fertilizer. But some plants might require more carbon dioxide (CO2) than is generally found in the air, and they might find it harder to develop in water. To create their own distinctive DIY systems for injecting CO2 gas into water, aquarists have experimented with a wide range of techniques, tools, schedules, and dose amounts. We at Aquarium Co-Op tested a number of them and created this straightforward tutorial to outline our go-to technique, which is dependable and easy to use.

Does CO2 get rid of algae?

Contrary to popular belief, CO2 does not immediately address algal issues. A healthy planted tank requires the proper levels of lighting, fertilizer, and carbon dioxide. CO2 is one of the components that plants need to thrive. Since many newcomers abuse light and fertilizer, adding CO2 might help keep the aquarium’s balance. Algae, on the other hand, will flourish in a tank with high lighting, CO2 infusion, but, for example, insufficient nutrients.

Do all aquarium plants need CO2 injection?

As was said earlier, CO2 is one of the essential building blocks for all aquatic plants. While scarlet temple plants could benefit from the extra CO2, they do not need it, some species, like cryptocoryne plants, do not. A third type of plants, which includes Blyxa japonica, dwarf hairgrass, dwarf baby tears, and other analogous carpeting species, requires stricter parameters for the highest chances of success.

Materials for a CO2 System

  • Aquarium Co-Op CO2 regulator

Describe a regulator. The amount of gas that exits the CO2 cylinder tank and enters the aquarium water can be precisely controlled with the help of a regulator.

What distinguishes a single-stage regulator from a two-stage regulator? In comparison to a single-stage regulator, a two-stage regulator lowers the gas pressure in the cylinder in two steps, resulting in a more reliable and steady flow of CO2. A two-stage regulator also helps prevent “end-of-tank dumps,” which occur when a nearly empty CO2 cylinder unexpectedly releases the remaining gas.

Do I need a pressurized CO2 system or a DIY CO2 system? The DIY systems we evaluated, which made use of yeast, citric acid, and other mixes, may have been less expensive, but they weren’t as dependable as pressurized CO2 systems, which made use of a regulator and cylinder. The inconsistent levels of CO2 created by DIY reactions, which frequently produce huge amounts of CO2 initially before falling over time, might make it difficult to balance a planted tank. Additionally, the reaction may be affected by temperature, the process takes a long time to maintain, and the pressure is not as high. With a pressurized system, we simply set it up once and let it run for one to three years without needing to refill the cylinder.

  • Aquarium Co-Op manifold block add-ons (Optional)

By adding up to five more manifold blocks to the system along with our regulator, you can increase the system’s capacity and run CO2 to multiple tanks.

  • CO2 cylinder tank

Will a CO2 paintball cylinder work? The Aquarium Co-Op regulator is not designed for use with paintball tanks. They can be used with tanks with male CGA320 threads that are common cylinder tanks.

A CO2 cylinder can be purchased where? Our preferred suppliers are the nearby welding and home brewing supply shops. If you return your empty CO2 cylinder, they frequently also provide CO2 refill services.

  • Airline tubing or CO2 tubing

Is special CO2 proof or CO2 resistant tubing required? We use Aquarium Co-Op airline tubing on all of our tanks because it is a flexible, black PVC tube that is safe for human consumption, and we have not noticed any observable CO2 loss. According to our experience, special CO2 tubing is more expensive, harder to bend, and less widely available.

  • Regular check valve or stainless steel check valve (optional)

Is a check valve necessary for my CO2 system? Check valves are used to prevent water from pouring over the regulator and spilling out of the aquarium when the regulator is turned off. Although the built-in check valve on the Aquarium Co-Op regulator’s bubble counter is already present, you might choose to install a second one as a backup. The common plastic check valves that we personally utilized with CO2 systems in our fish store, warehouse, and homes did not decay. Despite this, CO2 eventually causes plastic to deteriorate, so we also offer a stainless steel option for greater durability.

  • CO2 diffuser

What kind of diffuser should I purchase? Any CO2 diffuser designed specifically for aquariums that can operate at roughly 40–50 psi should work just fine.

If a CO2 diffuser gets blocked, how do I clear it? Diffusers eventually require cleaning or replacement due to the buildup of algae. Diffusers can be made of a variety of materials, so follow the manufacturer’s instructions when using diluted vinegar, bleach, or other cleaning agents.

  • Water or mineral oil

To see the approximate pace at which CO2 is entering the aquarium, fill the bubble counter with regular tap water. Mineral oil can be used in place of water since water will evaporate over time, meaning you never have to refill the bubble counter.

  • Electrical outlet timer
  • Adjustable wrench with at least 1.25-inch width
  •  Scissors
  • Spray bottle with water and a few drops of Dawn dish soap

How to Install a CO2 System

Once you have everything you need, we advise that you follow the thorough instructions in our handbook and video lesson. This high-level diagram demonstrates how each component is connected and will assist you in visualizing the overall CO2 system:

  • The regulator (B) screws onto the CO2 cylinder (A).
  • Optional manifold block add-ons can be added to the regulator (B).
  • The bubble counter (C) on the regulator is filled with liquid, and airline tubing is attached to the lid of the bubble counter.
  • The airline tubing connects to the diffuser (D), which is placed at the bottom of the aquarium.
  • The optional check valve (E) is installed in line with the airline tubing near the aquarium rim.
  • The regulator’s solenoid valve cable (F) is connected to the power adapter (G).
  • The power adapter (G) plugs into the electrical outlet timer (H), which plugs into a wall outlet or power strip.

Is it bad if the CO2 bubbles from the diffuser are reaching the water surface? This is not abnormal. Your diffuser should be positioned as low in the aquarium as you can. The CO2 gas is being absorbed into the water as the diffuser releases bubbles, which gradually get smaller and smaller as they rise.

How Much CO2 to Dose

We recommend setting the regulator to around 1 bubble per second (i.e., the pace at which CO2 bubbles move through the bubble counter) in the manual since we would prefer to begin with a lower level of CO2 to keep the fish safe. The bubble rate, however, is not a precise method of measurement because each aquarium has a different degree of fish and plant stocking, which causes variations in the CO2 dosing volumes for each tank. Additionally, rather than using drop checks to try to reach the “ideal” number of 30 ppm of CO2, we directly listen to nature and the plants when they let us know when they are satisfied.


Leave a Comment

Hikari Tropical Discus Bio-Gold Fish Food, 2.82 oz (80g)

• Natural color enhancing ingredients safely produce brilliant colors
• Highest grade of caroteniods available today to help your fish look their best
• High in stabilized vitamin C to support immune system health
• Perfect blend of proteins, amino acids, vitamins and minerals
• Free of parasites and bacteria common with live foods

Fluval Canister Filter, FX6 Filter (400 Gal)

Designed for aquariums up to 400 gallons, FX6 is the high-capacity workhorse of Fluval’s canister lineup, enhanced with all the power and reliability you’ve come to expect from a high-performance filter.