How to Use Liquid Carbon in Your Planted Aquarium

Live aquarium plants require carbon dioxide (CO2) to photosynthesise and generate 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 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. Most of these products contain glutaraldehyde and similar chemicals that are known to decrease algae growth in a planted aquarium. Aquatic plants grow faster and more healthy when there are fewer algae competing for nutrients, light and carbon dioxide.

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. 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. Some initial studies have analyzed how much CO2 is released from recommended doses of liquid carbon, and the numbers were significantly lower than 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 distinction between liquid carbon or activated? Both are used in filtration systems. Activated carbon is a type of filter media that specifically traps medications, tannins, and other impurities from the water.

Is liquid carbon dangerous to humans? Treat glutaraldehyde as carefully as you would treat bleach. The liquid should not be swallowed, inhaled, or touched. Rinse it off if you have it on your skin. 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 algicide that we use to control algae growth in 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 contains 1.5% glutaraldehyde and 0.5% citric acid, and a 16 oz (500 ml) bottle treats 5,000 gallons of water.

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. Use the same dosage on a daily basis for medium to high light aquariums. If in doubt, lower the dosage and increase it after two weeks of evaluating its effects.

Liquid carbon can also be used for spot treatment on stubborn algae like black beard algae. To test the Easy Carbon, shut off the circulation pump and filter. After a few minutes, you can turn on the filter again. 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. Do not overdose the tank beyond the recommended amount of liquid carbon or else the plants in the aquarium may be adversely 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. The water can be removed by regular water changes or improved mechanical and chemical filtering.

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.

Your aquarium may have low levels of nitrate, which is typically between 0-5ppm. If this happens, you should consider adding Easy Green all-in one fertilizer to your tank according to the instructions. 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. We wish you the best with your tank and all that you do is to enjoy the beauty of nature every day.