How to Use Liquid Carbon in Your Planted Aquarium

Live aquarium plants require carbon dioxide (CO2) to photosynthesise and generate energy. Hobbyists use CO2 gas to increase plant growth speed in high-tech planted tanks. But what if you don’t want to deal with expensive CO2 injection systems? 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 for more information about liquid CO2 and how you can best use it to grow your aquarium.

What is Liquid Carbon?

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. These products almost all contain glutaraldehyde, or similar chemicals. This is known to decrease the growth of algae in an 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. People have set up tanks with high-tech technology to inject more CO2 gas into water. The concentrations can be anywhere from 10-30ppm. Initial studies showed that liquid carbon has a lower level of CO2 than the recommended dosage. In fact, an aquarium that has good surface agitation, gas exchange with an air stone, or filter, results in about 3-5 ppm of CO2 in the water. This is much higher than what liquid carbon seems to provide.

Liquid carbon is often sold as a replacement for pressurized CO2 gas, but we find it more useful as an inhibitor of 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. Rinse it off thoroughly after you have applied it to your eyes and mouth for at least 15 minutes. For USA customers, reference the poison.org website. For Canadian customers, reference dpic.org.

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 LiquidCO2 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 should I use liquid carbon? Dosing with Easy Carbon is very simple, since the bottle already comes with a pump head. 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.

Spot treatment of stubborn algae, such as black beard algae, can be done with liquid carbon. 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. 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.

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 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. 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. Use a power outlet clock to reduce the amount of lighting you use each day. After that, wait at least 2 weeks for results.

If your aquarium consistently has very low nitrate levels around 0-5 ppm, your plants may not be getting enough nutrients, so trying dosing some Easy Green all-in-one fertilizer according to the directions. 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.

Find out more about plant nutrients in our article on selecting the best aquarium fertilizer. Enjoy your garden and the outdoors every day.