Does CO2 get rid of algae?

Some claim that the most effective way to control algae is to provide the tank with sufficient amounts of CO2. This will come either via CO2 injection or via chemicals like CO2 tabs and liquid CO2. This may sound a bit bold but a lot of experienced aquascapers swear by it. They know through experience that while CO2 supplementation is not an overnight miracle cure it works beautifully long term. Adequate CO2, along with sufficient filtration and good husbandry is the only thing that will prevent the algae from growing and becoming a menace to the tank. There are dozens of chemicals that can kill algae. Numerous methods have been developed to eradicate algae in the aquarium, but none apart from the things mentioned can effectively prevent them from ever coming back.

Does CO2 get rid of algae?

What is algae?

Algae is enemy number one for the planted tank. It is the most stubborn problem a hobbyist is likely to encounter in his aquascaping ventures. The way CO2 works is that it makes the plants healthier so the plants can then compete with the algae for food and space. CO2 is one of the essential components of photosynthesis. Providing sufficient amounts in the tank would greatly increase the aquatic plants' chances to be healthier. Healthier plants grow way faster than weak ones. If they grow at a much faster rate they would grow in mass and so would absorb more nutrients and fill up space therefore competing with the algae.

Algae is a plant too!

Algae, bear in mind, are plants too. They have the same requirements as plants. They also manufacture food (photosynthesis) like plants do. They will also require CO2 to do photosynthesis. They will also benefit from the CO2 injection. They will also benefit from the excess nutrients in the tank. That is why they are so hard to eradicate because everything they require are required by plants as well. So, the hobbyist cannot simply take away algae’s requirements to stop them from reproducing because then he would be taking away what the plants need to grow. Taking away light and nutrients are simply out of the question. It would also affect the plants and would make them unhealthier.

How to get rid of algae in an aquarium?

As mentioned in the introduction, there is no way of getting rid of algae in aquarium during a short period of time, and actually, it's not possible 100%. However, there are some factors you can take into account if the algae outbreaks are frequent.

Use a lot of plants if you want to fight algae

The good thing about algae is that they are tiny. They can be outcompeted by plants if there are more healthy and growing plants to begin with. That is why it is advisable for newbies to pack the tank with plants, to begin with, and provide CO2 supplementation so plants can grow algae-free and healthy. How many plants? As many as the design allows. An effective aquascaping design would allow a minimum of 50% plants. Some designs even allow showing only portions of exposed wood or rocks. The rest are covered in plants. This is not only done because the tank will look good with a lot of plants.

Does CO2 get rid of algae?

CO2 injection impacts the water chemistry

Enough CO2 injected into the water will also make the water slightly acidic. This also makes the plants healthier. A lot of the plants being used for aquascaping were collected in swamps and marshes and forest streams where waters are soft and slightly acidic due to tannins and decaying matter. Tank pH will actually swing from neutral to acidic when the CO2 injection is turned on. When the CO2 is turned off at night, the water pH will swing back to neutral. Some algae are known to dislike pH fluctuations and some hate acidic water. The most common types of algae found in tanks do luckily belong in this group.

The BBA - nightmare of the aquarium hobby

One kind of algae seems to be an exception to this. The Black Beard Algae is normally found in areas where there is flow and with light levels of CO2. They seem to thrive on inconsistent CO2 being mixed into the water. They are usually found in canister filter outlets where inline CO2 diffusers are used. They are not found growing on glass and ceramic diffusers though as oftentimes there is no sufficient flow in them. If we dig deeper though, we will find that CO2 is not the only thing that triggers Black Beard Algae. The cause of algae growth in the aquarium environment usually is a combination of high flow rate, too much rotting vegetation and detritus in the tank and a high level of iron in the water column. Take away one of these triggers and the BBA problem will go away on its own. Usually, it is the rotting vegetation and detritus that is cleaned and iron levels are adjusted but never the CO2. Adjusting CO2 levels to lower than the recommended level will actually do more harm than good. It makes the plants unhealthy. Unhealthy plants always will equal algae, if not now then in the long run. Never take focus off of the plants while trying to combat algae.

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Free-floating algae

Some less-known types of algae are actually found in acidic waters. They thrive in acidic environments. Luckily. These types of algae require some things which are not found in the planted tank environment. Some are known to thrive in alkaline environments. Green water are free-floating algae that seem to thrive in alkaline water that are in bright spots. They usually are found in ponds and pools. When the pH of these ponds becomes more acidic though, they would cease to thrive. This is also the case for some species of hair algae as well.

Does CO2 get rid of algae?

So does CO2 get rid of algae aquarium-related problems?

When used under normal circumstances, CO2 alone cannot be the sole treatment for algae. It certainly does contribute a lot to get rid of algae. Having a tank with a great regular maintenance routine, great filtration and water flow and adequate levels of CO2 in the water during photosynthesis is the best way to prevent algae from ever growing out of control. Some say there really is no way to get rid of algae 100%. The hobbyist’s job is to limit algae growth so it will not be visible in the tank.

Liquid carbon dioxide

Some people claim that using products labeled as liquid CO2 can treat algae problems. It is done by spot-dosing the chemical on areas with algae problems. Spot dosing is just one way of ensuring that the plants get sufficient carbon to use in photosynthesis. This is also another way of temporary overdosing. While overdosing plants temporarily with CO2 does not have an effect, it seems to be successful in algae control. Not all tanks will react to this spot dosing though. Some tanks that are too unbalanced will never react to a single solution. Fixing the issues would be the best course of action.

Lighting & ferts

Adjusting the light is first. The lights might be too bright. Monitor temperature as well. Make sure they are constantly within range. Adjust the dosing of fertilizers and if possible, do spot doses on fertilizers as well. For most algae found in planted tanks, manual removal is the best course of the initial action.

How to remove algae from aquarium in the best way?

Remove as much of the algae and not try to rely on chemicals to kill it. Killing algae without trying to remove it from the tank would only mean there will be plenty of decaying matter inside the tank. Dead things in the tank water are always bad. Never rely on the biological process to clean this out.

Does CO2 get rid of algae?

Get some knowledge and don't neglect the problem!

Whatever the cause of the algae bloom may be, please bear in mind that reversing the effects is sometimes more difficult than actually trying to prevent it from ever happening. Nowadays, information is free. Please take the time to read some and continue reading more about these topics. No one is an expert when it comes to algae. An experienced world champion aquascaper could suddenly find his tanks filled with algae if neglected for a few days. Most experienced aquascapers though know not to let the problem get out of hand and nip it in the bud while the problem is still young and sometimes the solution is as simple as taking that piece of algae out of the tank. The aquarist will know if what he has in his tank is the start of full-scale algae bloom and he or she wants to reduce algae in aquarium environment drastically or this is only a minor problem. This is how important experience is.

If you'd like to learn how to fight algae in aquarium, visit this ARTICLE


If you'd like to learn how to use liquid carbon in your planted aquarium, visit this ARTICLE


Please bear in mind that there is no overnight cure for algae. An algae-ridden tank did not grow those algae overnight and so treatment is not a one-time application. It usually is in the course of a few days and sometimes even weeks. Usually, correcting the mistake does not show instant results. That is why there are guidelines posted on the web regarding how to prevent algae in aquarium, so the hobbyist will know how to cure the problem before it started. This hobby in general requires patience as is with any hobby involved in growing plants such as Bonsai or flower gardening. One simply cannot expect flowers when the seeds were just planted yesterday. Trust in the literature but more importantly learn from the mistakes. Not all outcomes are found in books and it is only through experience in algae problem in aquarium hobby that the scaper will learn and eventually be good at something.

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