Once you are done setting up an aquarium, the first thought that comes in your head is how can you grow the aquatic plants faster and make them healthy so the fishes living in the aquarium can have a safe habitat.

Unlike humans, CO2 is very important for plants to grow. And with a proper supply of CO2, you can grow the plants multiple times faster. You can add CO2 in many ways to your planted aquarium. The most helpful and popular way is using a tank filled with pressurized CO2 with a regulator mounted on it with a diffuser added to the system.

These terms might sound a bit strange but stay tuned as I enlighten you about how to add CO2 to your planted aquarium using these components.

Components you need to add CO2 to your planted aquarium

The type of CO2 that I will describe is pressurized CO2. Adding this type of CO2 requires a complete system. But don’t you worry, cause I got you covered from the components to the whole procedure. In order to add pressurized CO2, you will need a few pieces of equipment. Those are given below.

How To Add CO2 To Your Planted Aquarium

1. CO2 Tank

There are CO2 tanks available of different sizes and different brands. According to the size of your aquarium, you should pick one. My suggestion would be to go for a larger one because with a bigger tank, the number of times you will have to refill it will be less.

2. Regulator

As you start the injection process, you will need this equipment. A regulator lets you adjust the pressure by using a knob while injecting. After opening a tank CO2 comes out very fast, and to control that rate you need a regulator. You can set the speed at how many bubbles you want to insert at a time.

3. Diffuser

Before entering your planted aquarium, CO2 goes through the diffuser. It breaks down the CO2 gas into bubbles so that the aquarium can easily absorb the CO2. You can place the diffuser at different places, but it would be best to place it on the other side of the outlet.

Read Next: Best CO2 Diffusers

4. Drop checker


With the help of this kit, you can check the amount of CO2 that has been added to the water. Bromothymol blue named solution is in this kit, which changes color according to how much CO2 you have in your water. If the color of the solution turns green, it means you have a sufficient amount of CO2 in your planted aquarium water.

5. Bubble counter

This component lets you know about the bubbles. It’s an external component used by some, to have a better understanding of bubbles. Whether the number of bubbles is right or not is understood from this device.

6. Solenoid

It’s a very simple yet important tool, especially for people who are fond of aquariums. When there’s no sunlight or lights, the photosynthesis process does not take place. So not much CO2 is needed at that moment.

In such moments, you can stop the supply of CO2 or lessen it. But you won’t be available in person all the time to do that. And this is where solenoid comes in. It will do your job when it senses there’s no light available.

7. Tubing

To connect the regulator with the diffuser, you need tubing. Make sure to buy the right kind of tubing which is designed to carry CO2. Otherwise, the CO2 might leak out.

8. Spanner

It is used to tighten the regulator, so there’s no leakage of CO2. Spanner is a kind of wrench.

Recommended Tools & Gear For A Planted Tank

Finding out how to add CO2 to your planted aquarium

Now that you know about the components needed in order to add pressurized CO2 to your aquarium, let’s see how by using those you can increase the amount of CO2 in the water. From start to end, the whole process is described step by step for your better understanding. Let’s look at the steps.

1. Connect the CO2 tank with a regulator

At starting both the valves of the tank and regulator should be closed and you should make sure that you have closed the precision knob as well. Now using the spanner, tighten the regulator nut with the tank firmly to make sure you leave no leakage.

5 lb. Aluminum CO2 Cylinder
5 lb. Aluminum CO2 Cylinder

2. Attaching Diffuser

Connect one end of the tubing you are using to the bubble counter and make sure you tighten it using a spanner. Then take the other end of the tubing and connect it to the diffuser. If your diffuser comes with any cap, unscrew that before connecting.

Precision CO2 Check Valve
Precision CO2 Check Valve
In-Tank Flux_ CO2 Diffuser
In-Tank Flux CO2 Diffuser

Always try to put the diffuser at the very bottom of the aquarium tank. This will allow the CO2 bubbles to travel the longest distance which is more beneficial.

3. Add tubing and fill bubble the bubble counter

First remove the covering of the bubble counter and fill it up with water and put the covering back on. And with the tubing connect the diffuser with the bubble counter. Lastly, beware of minerals getting inside the bubble counter.

4. Open all the valves

Now that you have connected all the components and placed everything where they are supposed to be, now it’s time to open the valves. Start with opening the valve of the CO2 tank. As soon as you open the valve of the tank, CO2 will start coming out at high pressure. Open the tank valve fully and control it with the regulator.

Pro-Elite Series The Most Advanced Aquarium Dual Stage CO2 Regulator
Pro-Elite Series The Most Advanced Aquarium Dual Stage CO2 Regulator

Using the knob on the regulator, keep the pressure at 20-30 psi if your diffuser is in the tank. In the case of a line diffuser, you need to keep the pressure at 30-40 psi.

5. Adding solenoid and adjusting bubble counter

After completing everything, it’s time to add the solenoid. Plug it into a timer and set a timer period for which the solenoid should work. You can adjust the time frame according to your preference. The best option that you can go for is to set the timer in such a way so that CO2 starts entering the aquarium an hour or so before the light comes and the CO2 supply is turned off an hour before the light source is out.

And to set the bubble counter, you should adjust the knob in a way that you can count the number of bubbles entering. There’s no specific rule about how many bubbles should enter per second. As long as your aquarium is not more than 75 gallons, 1-2 bubbles every second is enough. And if you find it necessary, you can increase the number of bubbles in future.

6. Check the drop checker

The drop checker indicates the CO2 level present in your water through colors. While deep blue means high ph and low CO2, yellow means low ph and high CO2. The drop checker will go green once your water reaches an adequate CO2 concentration.

CO2 Drop Checker Kit
CO2 Drop Checker Kit

Keep in head, the drop checker refers to the CO2 level of the previous hour. It takes almost an hour for the drop checker to analyze the CO2 level.

Why adding CO2 in your aquarium is important

CO2 is extremely essential for aquatic plants. Without it, photosynthesis can’t happen, and without photosynthesis, plants can not produce their necessary foods. We all know without proper nutrients no life can grow.

So, to make sure that the plants in your planted aquarium are growing fast, you need to provide a sufficient amount of CO2. Usually, in your typical tap water, the amount of CO2 present is around 3-5 PPM( parts per million). But you should maintain a 25-35 ppm level in your aquarium.

A few points are briefly mentioned for your better understanding of the importance of CO2 in your aquarium. Let’s look over those.

1. Healthy growth of plants

The plants living in your aquarium won’t just grow by getting sunlight. While sunlight is very important for healthy growth, CO2 is necessary as well. Without adding CO2 the plants might grow a little, but it won’t sustain. To make sure they are growing in a healthy way, adding CO2 is a must.

Interesting Read: No CO2 Carpet Plants- Is That Possible?

2. Equilibrium of CO2

Though the plants are getting lights on a regular basis, they may face CO2 deficiency. Because the CO2 of air can’t just get inside the water, so you need to insert it from time to time in order to maintain the equilibrium. As the plants are using the CO2 present in the water, there’s a demand for CO2 is creating as well. By adding CO2, you will meet that demand, and the plants will keep on growing.

3. Brings out the true color

We add various plants in the aquarium for the fishes mostly, but for the aesthetic of the aquarium as well. And in order to achieve that, you need to bring out the true color of the plants that you added. Often the deficiency of CO2 makes the plants a bit pale. When the plants receive an adequate amount of CO2, the true colors will be there to make your aquarium look more elegant.

4. Enhance the carpet plants

A lot of aquarium owners use carpet plants in order to increase the aesthetic of their aquariums. If you are one of them and the carpet plants you have added are struggling to form a nice carpet, maybe your aquarium has a lack of CO2 as well. Because carpet plants require a lot of CO2, and without that, they won’t be looking half as attractive as you want them to.

Maintaining the balance of CO2

Reading all the importance and beneficial factors of CO2, don’t start injecting as much CO2 as you can. Remember CO2 is important, but overdosing may cause various issues. Starting with causing death to the living animals and fishes in your planted aquarium as the oxygen level will decrease because of excess CO2.

On the other hand, the amount of CO2 depends on a few factors like the rate of flow, the volume of the surface, and how many plants you have, etc. This is why you should always monitor with a drop checker and make sure it’s showing green color.

Signs of too much CO2 in aquarium

If you are wondering apart from the drop checker, is there any way to know whether your aquarium might have an excessive amount of CO2. Well, there are a  few, and they are very simple. All you need to do is observe.

First of all the sign that you are going to notice is the change of behavior among your fish. If you have noticed the behavior of fishes in your planted aquarium before, you will see changes if the CO2 amount is excessive. The fishes will continuously come near the surface and gulp air, which indicates they are not getting enough oxygen. Sluggish behavior and less interest in eating also indicate that your aquarium might have too much CO2.

If you see erratic movement and less consciousness or dead fishes in your aquarium, that surely indicates that you need to do something to reduce CO2 in the aquarium as soon as possible. The PH and KH ratio also indicates CO2 conditions in your planted aquarium.

How to make a DIY CO2 supply

If you have a very small aquarium, and you don’t want to spend big bucks on pressurized CO2, I have this awesome option for you. It’s a DIY CO2 system, which you can build with very few basic elements.

After determining the amount of CO2 you will be needing, you need to pick the size and how many bottles you are going to use.

For an aquarium that is small, two 2L bottles are enough. A few things which you will be needing in order to make CO2 on your own are bottles, sugar, yeast, bubble counter, suction cup, water, scissors, super glue, diffuser, sodium bicarbonate and a few things which you will surely find in your home.

Liquid CO2 for aquarium

Liquid CO2 also works as a very good plant fertilizer for planted aquariums. It’s also helpful in controlling algae growth in your aquarium. To balance the light, nutrients, and CO2 levels in your planted aquarium, you can use liquid CO2.

Liquide carbon comes in a bottle, and you simply need to dose it in your aquarium. Pumping 1ml for every 10-gallon water every day is well enough for your plants to grow faster. And like other CO2s, don’t overdose liquid CO2 as it might be harmful to the fish. Try to apply the liquid carbon every day at the same time, best if you apply just before the light source activates.

Overall it’s a very cheap and easy solution to your problem. And you don’t need any expert help with this. As long as you have a small aquarium, this is an ideal solution for you.

CO2 tablets for aquarium

CO2 tablets are another amazing solution to the crisis of CO2 in your planted aquarium. These tablets are basically CO2 in tablet form, which dissolves and adds CO2 to your aquarium once you drop them inside.

Usually using one tablet each day for 8 gallons of water is standard. They are the easiest way to provide oxygen to your planted aquarium. You will be saving a lot of time using CO2 tablets. It stabilizes pH level in your aquarium and also fights algae.


Now that you know how to add CO2 to your planted aquarium, watch and see how your plants grow faster than ever once you complete the whole process. Just be mindful about not injecting too much CO2, for that purpose make sure you add a drop checker.

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