How To Add Carbon Dioxide To Aquarium In 4 Easy Methods

CO2 System for Aquarium
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Last Updated: July 13, 2022 by Flora Gibbins

CO2 is necessary for replenishing plants in an aquarium and creating a natural nutrients cycle. It’s also an essential factor in the pH balance of water that can affect your fish’s well-being.


There are many ways to provide carbon dioxide in an aquarium. This post will go over several popular methods that can help you grow plants and keep your fish happy.

We will explain how each of these methods works to choose which one is right for you. So read on, fish friends.

Different Methods of Adding CO2 to Your Aquarium

Pressurized CO2 Systems

Pressurized CO2 Systems

A pressurized CO2 system is the most efficient and effective way to get carbon dioxide into your aquarium. It’s what you see at a commercial fish store, and it’s a bit more complicated than the other methods. 

It requires you to hook up a pressurized tank of CO2 to something like a bubble wand or diffuser. The overall process is quite involved but also very reliable and effective.

You will need a regulator that releases and add carbon dioxide into a bubble wand (this part looks like an upside-down turkey baster), then an outlet on the wand that lets water flow through it. The outlet will have a nozzle that drops the carbon dioxide into the water.

The bubble wand is usually placed near the water’s surface and meets the air. The carbon dioxide bubbles are heavier than air and fall to the bottom, displacing some of the oxygen at the aquarium’s surface. 

Knowing how to get CO2 in an aquarium helps increase your planted aquarium dissolve oxygen content and provides many other benefits to your fish, like filter-feeding triggers and reactions.

Pressurized CO2 systems fill a tank, release it via a regulator to lower pressure, and send it to an exit where you may adjust the flow rate using a solenoid valve. Higher settings give plants more CO2.

If you are using a pressurized tank of carbon dioxide, you must put it in a separate room from your home. You do not want to breathe any CO2 fumes and risk being poisoned. 

In addition, a tank full of flammable carbon dioxide gas is not something that should be used without protection from fire or explosion, even if it is in an isolated room or closet (that’s why we don’t recommend using your house for this purpose).

The downside of using a pressurized system is the price (the tanks can run several hundred dollars), which obviously requires electricity. The upside is that you are guaranteed to get the carbon dioxide you need for your aquarium, and the process is pretty automated.

Yeast Based Systems

Yeast Based Systems

This system uses yeast that processes sugar and produces CO2 as a byproduct. You add the yeast to water and feed it sugar, and then it releases CO2 for your fish’s aquarium plants without any additional work on your part. 

This method is suitable for beginners because it requires little equipment or initial setup time. The two problems with this type of system are that you have to replace your yeast after several months (or sooner if you’re using tap or chlorinated water), and also, yeast doesn’t produce as much carbon dioxide as other methods do.

Although this type of system is fairly inexpensive, it requires some initial setup, so it’s not as good of a deal as the pressurized system.



Aerosols are a trendy and easy way to aerate your aquarium plants without using electricity. You can buy them at most pet stores. There are several different types, including DIY spray rigs and commercial machines. 

The aerosol machines create an aerosol mist that is released into your aquarium and then hits the water’s surface below. The extra carbon dioxide in the tank will rise with the carbon dioxide gas and then release into a diffuser or bubble wand for your aquarium plants.

The downsides of this method are the noise and mess. It can be noisy and depending on how many UV lights your planted aquariums have, it may become quite a mess from fish waste. Fluid can also get into your tank if you don’t have a good seal.



Doing something like this is pretty straightforward, but it does require some basic knowledge about gases and chemistry and some time to do it right. You will be fine if you’re comfortable doing plumbing or electrical work.

You will need a four-liter bottle of carbon dioxide and a two-liter potassium hydroxide (KOH) bottle. 

You mix the two chemicals, and for every liter of water in your aquarium, you’ll get about five milliliters of solution. Mix it up in a bucket and immediately drain the solution into your aquarium.

It would be best to use a diffuser/bubble wand to filter out CO2 from your air. It doesn’t work as well as using pressurized CO2 because you are using air from outside the tank to bubble along with extra carbon dioxide from inside the tank; nonetheless, it does benefit fish without setting up a pressurized system or purchasing expensive equipment.

Proof That CO2 Works

The truth is that there’s no definitive way to measure the benefits of CO2 injection into an aquarium. Everything from sunlight to fish movement to temperature affects plant growth. 

So it is impossible to say for sure if the fish are receiving more nutrients or if the plants themselves are growing better because of it. This will help you learn how to inject CO2 into the aquarium effectively. However, there are ways you can prove that it is effective. 

If a DIY system is working correctly, then there should be a noticeable fair of CO2 being released into the tank, and there should be bubbles coming up from the bottom of your tank and around your plants. 

This can be tested by looking at your plants. If you get results like these, then it’s a strong indicator that your system is working properly. You can also go ahead and learn how to put CO2 in an aquarium.

Why Is CO2 So Important For Aquatic Plants?

The chemistry between carbon dioxide and oxygen is essential for aquatic life. The photosynthesis process converts CO2 from the water into carbon compounds used as food by aquatic plants.

When this process occurs, there’s a little leftover. What’s left is part oxygen and part carbon dioxide; it is what powers the chemical reaction in your aquarium. If there is not enough of it, the photosynthesis process breaks down, which leads to less plant growth and, eventually, even death.

To overcome this problem, you need to give your plants extra CO2 to continue their growth cycle without any disruptions or reductions in their rate of photosynthesis. You can also solve this problem by learning how to add CO2 to the aquarium correctly.

CO2 is an essential part of the aquatic life in your tank. It is used by almost all plant species and helps to support their life cycles and feed them.

If you fail to add CO2 when needed, then your aquarium will lack sufficient nutrition and carbon dioxide levels that can keep fish very weak, causing them to die. 

If you fail to add CO2 when required and keep it at the correct carbon dioxide levels, some pump types may not function properly, and other parts could get damaged, leading to issues such as your pump not operating properly or broken parts.

To know how to increase CO2 in aquarium, CO2 can be bought in many different sizes suitable for all types of aquarium tanks, including aquatic planted tanks. There are small glass bottles that hold 0.4 to 0.6 pints of CO2 for use in aquariums and a large glass tank that holds 1.8 to 2.6 pints of CO2 for use in aquariums.

What Is A Bubble Counter?

You will notice that when your aquarium is in use, you will usually see bubbles coming up from the bottom or sides of your tank due to CO2 injection. These bubbles are used to aerate the water and oxygenate it for your fish. 

Bubble Counter

A bubble counter is a device that measures the amount of carbon dioxide used by your plants.

You can measure that the bubbles are used correctly by purchasing a bubble counter at most aquarium stores or online. 

When you buy a bubble counter, it should have some way to hold it in place on the inside of your tank while still allowing you to change its position as needed. It’s a good idea to move it from left to right and up and down as you continue to readjust your system. 

Keep an eye on the bubbles that are going in and out of it to notice if there’s something wrong with your system or if something is starting to malfunction. 

If that happens, there’s a good chance your fish might not be getting enough oxygen or might be getting too much CO2 in the water. In such a case, there will be the need to increase or reduce CO2 injection in the tank.

Turning on the Gas Supply Safely

If you turn on the gas from the source, it’s a good idea to turn off the electricity at the same time. Gas-powered air pumps have a fuel-injection system that can ignite if there is an electrical short.

If you elect to use electricity for your CO2, ensure that all of your electrical connections are secure and in good working order. 

You might also be advised to cover all of your electrical connections with plastic wrap or tape. 

Never, ever leave anything around an electrical outlet without covering it up. If there is any gas leak in your planted aquarium and it’s blown into one of these areas, it could ignite with little to no warning.

To ensure a tight seal around your tubing, use a plastic zip tie to secure it to the tank. The connection should be snug without the possibility of gas leakage. Take care when cleaning the tubing because it can cause damage if there are any cuts or even small tears present. 

It would be best to keep it in good condition to avoid interruption in its flow while your planted aquarium is on.

How Do I Inject Carbon Dioxide Into My Aquarium?

There are many ways to inject carbon dioxide into your aquarium. If you’re going to get an air pump, you should also consider getting a CO2 tank capable of holding gas longer than a day. 

You want to make sure that you can maintain the necessary carbon dioxide level in your aquarium at all times. If you don’t, the fish will not get the nutrition they need and eventually die.

To learn how to add CO2 to an aquarium naturally, you’ll need instructions on how much to fill your tank up with to have enough supply for a certain amount of time. Once it’s filled up, make sure to turn off the electricity at the same time because there might be an electrical short if there is a gas leak.

When you add bubbles to your planted aquariums, make sure that you check the water level every hour, so there’s no disruption in gas flow. If the water level is higher than it should be, turn it off immediately. 

If you don’t, there is a risk that the gas pressure in your planted tank will not be high enough to keep up with its demand and could lead to an explosion.

These aquatic plants do not grow much faster with extra light, but the leaves, because they grow so slowly and live so long, eventually collect algae. Basically, in an aquarium with low to moderate lighting, the fish food you put in the planted aquarium can probably provide enough of the macronutrients.

If you are unsure of the best time to add carbon dioxide, you can do a visual check on your plants to see if they are lacking carbon dioxide supplementation. Some inhabitants may also have adverse reactions to carbon dioxide supplementation. There will be enough remaining CO2 in your aquarium for your plants during the last hour of your photoperiod.

Carbon dioxide enters the water from the atmosphere through the solenoid valve, from fish respiration, and from various other microbiological processes that naturally occur in a planted fish aquarium. So by adjusting the pH value, you can control the amount of CO2 in your aquarium.

The needle valves can be delicate, so be patient when fine-tuning. Monitor the drop checker for a few hours. Check what color is showing, dark blue means high pH/low CO2 while yellow indicates low pH/high CO2. Adjust the CO2 needle valve until the liquid turns green.

Fun Fact: Injecting carbon dioxide helps in improving your aquarium water’s pH level. The next issue is to deal with filters. Do your guppies need them or not? Read our article, “Do Guppies Need A Filter? We Separate The Dos And The Don’ts!” and find out.

Watch This!


CO2 is a fairly simple thing to add to your aquarium, but it’s essential to do it safely and learn how to add co2 to the aquarium naturally. It can help fish live longer, healthier lives, and plants will grow with or without CO2. 

You can learn various methods on how to get CO2 in an aquarium properly and choose the one that works for you. You don’t have to use a pressurized system if you can’t afford it; many DIY options work well.

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