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 often use pressurized CO2 gas in high tech planted tanks to boost the speed of plant growth, but what if you don’t want to mess with an expensive 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. Continue reading to learn more about liquid carbon and how it can be best used in your planted aquarium.

What is Liquid Carbon, exactly?

Many aquarium companies offer liquid carbon as part of their plant fertilizer collections. Liquid CO is also known as liquid carbon dioxide and liquid CO. It may be sold under the brand names Seachem Flourish Excel and API CO2 Booster in the United States. 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.

Does liquid CO2 replace pressurized CO2 gas? While liquid carbon is often marketed as a source of carbon, many planted tank experts agree that it is a poor replacement for CO2 gas. It is much easier and quicker to get CO2 directly from the air than it is to grow aquatic plants with their leaves out in water. 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 filter media that captures impurities such as medications, tannins, or other chemicals from water.

Is liquidcarbon dangerous for humans? You should treat glutaraldehyde with the same care as bleach. Do not swallow, inhale, or touch the liquid. It should be rinsed off any liquid that gets on your skin. If you get it in your eyes or mouth, rinse thoroughly for 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 that we use to help us when we’re in the process of balancing the light and nutrient levels 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 is made up of 1.5% glutaraldehyde (500ml) and 0.5% citric acids. It can be used to treat 5,000 gallons.

How often do I need to use liquid carbon? Easy Carbon can be used as a daily supplement. The pump head comes with the bottle. Dose 1 pump (1 ml) of Easy Carbon per 10 gallons every other day for low light aquariums. Medium to high-light aquariums will require the same daily dosage. When in doubt, start with a lower dosage and increase the dosing after evaluating its effects for two weeks.

You can also use liquid carbon to treat stubborn algae such as black beard algae. As a test, turn off the circulation pumps and filter. Use a pipette with Easy Carbon to spray some leaves underwater. After a few minutes you can turn the filter back on. In 4-7 days, the algae should show signs of discoloration and weakening if it has been affected. You can try a second spot treatment the following week if the first one is unsuccessful. Do not overdose the tank beyond the recommended amount of liquid carbon or else the plants in the aquarium may be adversely affected.

Which plants are sensitive to liquid carbon? Certain plants, like anacharis and vallisneria, are notorious for melting away in the presence of liquid carbon. If you have sensitive plants like these, consider dosing at half the recommended amount.

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

Why does my tank get cloudy water after using liquid CO2? Because liquid carbon is killing off algae, little particles of dead algae may detach and float into the water column. Regular water changes and improved mechanical and chemical filtration can help remove the particles from the water.

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. You can reduce your daily lighting by using a power outlet timer for 2-hour increments. Wait at least two weeks before you make any major changes.

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.