How to Use Liquid Carbon in Your Planted Aquarium

Live aquarium plants require carbon dioxide (CO2) to photosynthesise and generate energy. Hobbyists commonly use pressurized carbon dioxide gas in high-tech, planted tanks to speed up plant growth. But what if it’s not feasible to install a costly CO2 injection system into your tank? Some companies claim that liquid carbon dioxide is an effective substitute for CO2 gases, while others insist 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 and How Does It Work?

Liquid carbon, also known as liquid carbon dioxide or liquid CO2, is offered by many aquarium companies as part of their plant fertilizer collection. It can be found in the United States as Seachem Flourish excel, API CO2 Enhancer, or our Aquarium Cooperative Easy Carbon. Nearly all these products contain glutaraldehyde (or similar chemicals), which are known to reduce algae growth in planted aquariums. The growth of aquatic plants is often faster and more efficient when there are less algae competing with nutrients, light, carbon dioxide and other chemicals.

Can liquid CO2 replace pressure-treated CO2 gas? Although liquid carbon is often promoted as a source for carbon, many experts in planted tanks agree that it is not a good replacement for CO2 gas. Many aquatic plants prefer to grow without their leaves in water. This is because it is faster and easier to access CO2 gas from the air. To help their underwater plants, high-tech tanks were built that inject more CO2 gas in the water. These concentrations range from 10-30ppm. Initial research has shown that the amount of CO2 released by recommended doses liquid carbon is significantly less than that produced from pressurized CO2. 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.

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 charcoal is a type filter media that traps chemicals, medications, and other impurities from water.

Is liquid carbon dangerous to humans? Treat glutaraldehyde as carefully as you would treat bleach. You should not inhale, swallow, or touch the liquid. If you get it on your skin, rinse it off. If you get it in your eyes or mouth, rinse thoroughly for 15 minutes. Refer to poison.org for USA customers. 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 Liquid CO2 in Planted Aquariums

Easy Carbon is an anti-algae agent that we use in order to balance light and nutrient levels within our planted aquariums. Easy Carbon will not work if the tank is not balanced to allow plants to outcompete the algae. Easy Carbon has 1.5% glutaraldehyde, 0.5% citric acid and 16 ounces (500 ml). It can treat up to 5,000 gallons.

How much liquid carbon should I be using? Easy Carbon comes pre-filled with a pump head. For low light aquariums, use 1 ml (1 ml), of Easy Carbon every other day. Use the same dosage on a daily basis for medium to high light aquariums. Begin with a lower dosing and then increase the dose after two weeks of testing its effects.

You can also use liquid carbon to treat stubborn algae such as black beard algae. Turn off the circulation pumps as well as the filter. As a test, spray some leaves underwater with Easy Carbon. After a few more minutes, you can switch on the filter. 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. The aquarium should not be given more liquid carbon than recommended.

Which plants are sensitive to liquid carbon? Certain plants, like anacharis and vallisneria, are notorious for melting away in the presence of liquid carbon. You might consider reducing the recommended dose for sensitive plants.

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

Why do my tanks get cloudy? Liquid carbon kills algae. This means that small particles of algae can attach to the liquid carbon and float into your 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. The best way to decrease your lighting is to use a timer that can be used on a power outlet. You should wait for at least 2 week before making any significant changes.

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.

You can find more information about fertilizers for aquarium plants in our article How to Choose the Right Aquarium Plant Fertilizer. Enjoy your garden and the outdoors every day.