How to use Liquid Carbon in Your Planted Aquarium


How to Use Liquid Carbon in Your Planted Aquarium

Living aquarium plants require carbon dioxide to create and photosynthesize energy. Hobbyists frequently use pressurized CO2 gas for high-tech plant growth. However, what if they don’t have the budget to invest in a CO2 injection system? Some companies claim liquid carbon dioxide is an effective substitute for CO2 gases, while others argue that it is a chemical treatment to get rid of algae. Keep reading as we discuss what is liquid carbon and how to best use it in your planted aquarium.


What is Liquid Carbon?

As part of their plant fertiliser collection, many aquarium companies offer liquid co2 (also known as liquid CO2 or liquid carbon dioxide). You may see it sold in the United States under brand names like Seachem Flourish Excel, API CO2 Booster, and our own Aquarium Co-Op Easy Carbon. Most of these products contain glutaraldehyde and similar chemicals that are known to decrease algae growth in a planted aquarium. The growth of aquatic plants is often faster and healthier when there is less algae competing with nutrients, light, carbon dioxide and other chemicals.

Is liquid CO2 a substitute for pressurized CO2? Many experts say that liquid carbon is not a good alternative to CO2 gas. In reality, many aquatic plants prefer to grow with their leaves out of water because it is easier and faster to directly access CO2 from the air. Therefore, people set up high tech tanks to help their underwater plants by injecting more CO2 gas into the water at concentrations ranging from 10-30 ppm. Initial studies showed that liquid carbon has a lower level of CO2 than the recommended dosage. In fact, a normal aquarium with good surface agitation and gas exchange using an air stone or filter results in approximately 3-5 ppm CO2 in the water, which is still higher than what liquid carbon appears to supply.

Although liquid carbon is commonly sold to replace pressurized CO2 gas (which we prefer), it can be more effective as an inhibitor for algae growth.

What is the difference between liquid carbon and activated carbon? While their names may sound similar, liquid carbon is used in planted tanks, whereas activated carbon is used for chemical filtration. Activated carbon is a type of filter media that specifically traps medications, tannins, and other impurities from the water.

Is liquid Carbon dangerous to people? Use glutaraldehyde the same way you would bleach. You should not inhale, swallow, or touch the liquid. It should be rinsed off any liquid that gets on your skin. Rinse it off thoroughly after you have applied it to your eyes and mouth for at least 15 minutes. Refer to for USA customers. For Canadian customers, reference

Is liquid CO2 harmful to fish? While we can’t speak for other manufacturers, Easy Carbon is safe for aquarium fish, shrimp, and snails when used as directed.

How to Use Liquid CO2 in Planted Aquariums

Easy Carbon is an algae inhibitor we use when we balance the light and nutrients in our planted aquariums. Unless the tank is balanced so that plants grow well enough to outcompete algae, the algae will keep coming back, no matter how much Easy Carbon is used. Easy Carbon has 1.5% glutaraldehyde, 0.5% citric acid and 16 oz (500ml). It can treat up to 5,000 gallons.

How often should I use liquid carbon? Dosing with Easy Carbon is very simple, since the bottle already comes with a pump head. Low light aquariums will need to use one pump of Easy Carbon (1 ml) every other day. For medium-high light aquariums, use the same dose on a daily basis. When in doubt, start with a lower dosage and increase the dosing after evaluating its effects for two weeks.

Liquid carbon can also be used for spot treatment on stubborn algae like black beard algae. Turn off the filter and circulation pumps, and use a pipette to spray a few leaves underwater with Easy Carbon as a test. After a few minutes you can turn the filter back on. If the algae has been affected, you should see signs of weakening and discoloration in 4-7 days. If spot treatment is successful you can target a few additional leaves for the next week. You should not give the aquarium more liquid carbon than is necessary. Otherwise, the aquarium’s plants may be negatively affected.

What plants are sensitive to liquid CO2? Some plants, such as anacharis or vallisneria are known for melting in the presence liquid carbon. You might consider doubling the recommended dose if you have sensitive plants.

While liquid carbon is safe for fish and invertebrates, certain plants like vallisneria may be more sensitive to it.

Why is my water cloudy after I use liquid CO2 to kill algae? Small particles of dead algae can float in the water column from liquid carbon. Water filtration that is both mechanically and chemically improved can remove these particles.

Why isn’t Easy Carbon getting rid of algae? If algae is not going away despite regular usage of Easy Carbon, then most likely the tank is too unbalanced in terms of lighting and/or nutrients. Try reducing your daily lighting schedule in 2-hour increments using a power outlet timer, and wait at least 2 weeks to evaluate the results before making another major change.

You may find that your aquarium has low levels of nitrate around 0-5ppm. This could indicate that your plants are not getting enough nutrients. Follow the instructions to apply Easy Green all in one fertilizer. If your aquarium always has above 40 ppm nitrate, you can reduce excess nutrients from the water by doing more frequent water changes, feeding less fish food, or moving some fish out of the tank.

For more information on plant nutrients, read our full article on choosing the right aquarium plant fertilizer for you. Best of luck with your planted tank, and enjoy nature daily.