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How To Increase CO2 In Aquarium (Complete Guide)

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by Jason Matthews



If you have aquarium plants in your tank, increasing the level of carbon dioxide can help your plants live and thrive.

CO2 supplements such as API CO2 Booster are the easiest way to add CO2 to your aquarium to promote the growth of high-light plants. These carbon-based products are easy to use and come with clear usage instructions. Adding more fish to your tank may also help produce enough carbon dioxide to support low-light plants, as fish typically breath in oxygen and release CO2.

Generally, the method you choose will depend largely on the light requirement of your plants. As you’ll see in this article, there are various approaches on how to increase co2 in aquarium tanks.

Increase CO2 In Aquarium like a pro using these 4 methods


Aerosol CO2 setups are a cheap and easy way to add CO2 to an aquarium. They are made up of a diffuser, a hose, and a pressurized CO2 can. The can comes with a button that prompts the release of CO2 gas into the diffuser when you press it. The gas moves from the diffuser chamber until the diffuser fills up with water, and the process repeats.

Aerosol sets are relatively cost effective, but they do have their own setbacks. For starters, the diffuser is not as effective at diffusing gas into the water as a ladder diffuser or ceramic diffuser. Once more, you have to refill the diffuser manually or else the aquarium will be left with no CO2. Poorly circulated or fluctuating carbon dioxide levels have often been linked to algae growth in planted aquariums.

Keep in mind that aerosols are designed for small to medium-sized aquariums, as the can tends to run out rather quickly.

Yeast-based Systems

You can also use yeast-based systems to increase CO2 in your aquarium. Like aerosol sets, these systems are also cost effective and run at relatively low pressure.

Yeast based CO2 systems rely on sugar and water to produce CO2 and alcohol, which is why they come as a kit with a screw-top canister and sachets. You use these items to create a fluid that in turn produces carbon dioxide gas when it ferments. A ladder-style diffuser helps to introduce CO2 into the aquarium.

Keep your system in a warm room for best results. The production of CO2 will begin slowly, from a few bubbles to several bubbles, before the process stops altogether. At this stage, you should rinse your canister and then restart with the spare sachets.

Related article: How to prevent algae in aquariums

Pressurized CO2 Systems

Pressurized CO2 systems are ideal for experienced aquatic plant growers. A set comes with either refillable or disposable CO2 canisters, and usually consists of a diffuser, some hose, a regulator valve, and pressurized gas bottle.

A knob on the gas bottle releases CO2, while the regulator valve controls the amount of CO2 flowing through the precision needle valve. There is usually a pressure gauge on the basic regulator indicating operating pressure, but a more advanced regulator is equipped with two gauges: one indicating the pressure in the gas bottle and the other showing operating pressure.

Some pressurized CO2 systems are also equipped with optional extras, like a solenoid valve placed in-line to close off the gas. When the solenoid is plugged into a plug-in timer, you can set it to automatically turn carbon dioxide on and off. Since plants produce carbon dioxide at night, this extra is not needed. A non-return valve helps to stop aquarium water from back siphoning when the gas is turned off.

Liquid Carbon

Many aquarium companies offer liquid carbon in their collection of plant fertilizers. Common brands include API CO2 Booster and Seachem Flourish Excel. These products often contain glutaraldehyde, which has been shown to reduce algae growth in planted aquariums. Without the algae competing for carbon dioxide, light, and nutrients, your aquatic plants get to grow healthier and faster as a result.

Dosing with liquid carbon is pretty simple. Just dose one pump (1ml) per 10 gallons regularly for low light plants or the same dose daily for medium to high light plants. If you are not certain, start slowly and then increase the dosage after two weeks.

Liquid carbon can also be quite effective on stubborn algae such as black beard algae. Turn the circulation pumps and filter off, and spray a small amount of liquid carbon on a few leaves underwater using a pipette. Turn the filter on again after a few minutes. Signs of discoloration should appear on the algae in four to seven days if the treatment was successful. Apply the same dosage on a few other leaves if the treatment works, being careful not to overdose the tank as this can severely affect your aquarium plants. If you have sensitive plants such as vallisneria or anacharis, consider using half the recommended dosage as these plants have been known to melt away when introduced to liquid carbon.

Natural ways to increase CO2 in your aquarium

If you have extra space in your fish tank, you can add more oxygen-breathing creatures to increase the level of carbon dioxide being produced. Fish usually produce enough carbon dioxide to maintain low-light plants and many fish can produce sufficient CO2 for medium-light plants.

Fish poop is also naturally rich in carbon dioxide. If your aquarium has minimal plants but many inhabitants, the plants will have a natural source of CO2 from the nutrient-dense waste. Carbon dioxide increases with bacterial respiration in your aquarium. This method is suitable for plants that need little to no amount of CO2.

Knowing how to increase CO2 in aquarium can help you revive your aquarium plants for a longer and healthier lifespan. However, it is important to note that although plants can get overdosed with carbon dioxide with no side effects, this is not the case with fish. Too much carbon dioxide may kill your fish, so it is always a good idea to invest in a kit with a CO2 test kit and a good precision regulator.

The recommended CO2 level for planted aquariums is between 15 to 30mg/l. For best results, combine with complete liquid fertilizer, a nutritious planting substrate, and plant growth-enhancing lighting. Also, be sure to keep pressurized CO2 bottles away from the reach of children as they are a safety hazard.


Jason Matthews

My name is Jason Matthews, and welcome to my website. When other kids were bragging about how their dog could sit and roll over, I was bragging about my latest Betta Fish and the cool sea castle I just added to his aquarium. 

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