How to Add CO2 to Your Planted Aquarium


If you've recently set up your planted aquarium, you're probably wondering how to maximize the growth and health of your aquatic plants.

The answer lies in implementing a CO2 setup, which is essential for their thriving. While CO2 may be harmful to humans, it plays a vital role in the life of plants.

CO2 is a major contributor to photosynthesis, the fundamental process for plant survival. By supplementing CO2, you can accelerate the growth of your aquatic plants in your aquascape by 5-10 times.

This is just one of the many benefits that come with using CO2 in a planted aquarium. Are you eager to discover more? Then let's delve deeper into the topic!

In this article, we will cover the following topics:

  • Understanding the significance of CO2 for your aquatic plants
  • Exploring the various types of CO2 setups available
  • Providing a step-by-step guide on setting up pressurized CO2
  • Offering essential tips for successful CO2 implementation in your aquarium

Why do you need CO2?

Understanding the significance of CO2 in planted aquariums is crucial for the optimal growth and health of your aquatic plants. Let's delve into the science behind it, albeit in a more engaging manner.

CO2 is a vital component for the process of photosynthesis in plants. Just like humans need oxygen to breathe, plants need CO2 to carry out their own metabolic processes.

During photosynthesis, plants utilize light energy, water, and CO2 to produce sugar molecules and release oxygen. These sugar molecules serve as a source of energy for plants, facilitating respiration and promoting overall growth.

Plants with a higher affinity for carbon, or those that can efficiently absorb and utilize CO2, tend to exhibit faster growth rates. By supplementing CO2 in your aquarium, you can provide an additional boost to your plants, resulting in accelerated growth and improved health.

While low-light/low-tech aquariums can rely on naturally occurring CO2 from fish respiration and organic breakdown, introducing additional CO2 can yield even better results.

On the other hand, for medium/high lighting setups, CO2 injection becomes a necessity. This makes CO2 supplementation vital for achieving optimal growth and vibrant aquatic plants in your aquarium.

High tech plants and CO2 injection

Let's explore why CO2 injection is necessary for high-tech plants in more detail. Don't worry, it's not as complicated as it sounds!

Healthy Growth:

High-tech plants typically require intense lighting conditions. To support their rapid growth, a significant amount of CO2 is needed. The relationship between CO2 and lighting intensity is crucial for proper plant development. By injecting CO2 into your tank, you provide the necessary resources for your aquatic plants to thrive, resulting in faster and healthier growth.

Balanced CO2:

In high-tech setups with increased lighting, the demand for resources, including CO2, is higher. However, natural diffusion of CO2 from the air into the water may not be sufficient to meet this demand. To maintain a balance and prevent a CO2 deficiency, injecting CO2 into the aquarium becomes essential. Achieving this equilibrium through CO2 injection helps create a stable environment and can also contribute to reducing algae growth.

Color Intensity:

CO2 injection has a remarkable effect on the coloration of aquatic plants. If you desire vibrant and intense colors, particularly in red aquatic plants, CO2 injection is crucial. While some low-light plants may exhibit modest growth without CO2, the difference in color intensity will be evident. Injecting CO2 enhances the visual appeal of your high-tech planted aquarium.

Better Carpet Development:

Aquarists often strive to create lush carpeted areas in their tanks. However, achieving a thriving carpet of aquatic plants requires ample CO2 supply. If you notice that your carpet plants are not growing as expected despite adequate lighting, insufficient CO2 levels are likely the cause. Supplementing CO2 through the injection can significantly improve the development of your carpeted plants.

By understanding these intricacies, you gain valuable insight into the importance of CO2 injection for a successful high-tech planted aquarium. Remember to research the compatibility of CO2 injection with your fish species before incorporating it into your setup to ensure the well-being of all tank inhabitants.

CO2 injection methods

There are two common methods for adding a CO2 setup to your aquarium: Pressurized CO2 and DIY CO2.

Pressurized CO2

Pressurized CO2 is the popular and sustainable method used in the aquascaping hobby. It offers simplicity and effectiveness in injecting CO2 into your aquarium. To set up a pressurized CO2 system, you will need the following equipment:

Required Equipment:

  • Regulator: This device controls the release of CO2 from the tank, ensuring a controlled and gradual injection into the aquarium. It features a gauge to monitor and adjust the CO2 pressure.
  • Diffuser: The diffuser allows the CO2 to enter the aquarium efficiently by breaking down the gas into misty bubbles. Position the diffuser opposite the outlet of your filter for better dispersion throughout the water column.
  • Bubble Counter: This external equipment is used to monitor the number of CO2 bubbles being injected into the aquarium, providing a visual reference of the CO2 flow.
  • Drop Checker: A drop checker is a specialized kit containing a solution that changes color based on the CO2 concentration in the aquarium water. By observing the color change, you can determine the ideal CO2 level.
  • Solenoid: A solenoid valve is an affordable and efficient device that can be connected to an electric timer. It automatically shuts off the CO2 influx when the lights are off, as plants do not require CO2 during periods of darkness.
  • Tubing: Use CO2-specific tubing to connect the regulator and diffuser, preventing CO2 leakage.
  • Spanner: A spanner wrench is used to tighten the regulator securely, ensuring a leak-free connection.
  • CO2 Tank: Choose a CO2 tank of appropriate size, considering the duration and cost-effectiveness. Options include CO2 tanks, soda line bottles, and paintball CO2 tanks. Remember to purchase the correct adapter to fit the regulator onto the chosen tank.


The DIY method is a budget-friendly option for those who want to try CO2 supplementation before investing in a pressurized system.

Here's what you'll need for a DIY CO2 setup:

  • Bottle: Use a suitable bottle as the CO2 generator.
  • Tubing: Select vinyl or silicone tubing to connect the bottle to the aquarium.
  • Suction cup: Attach the tubing securely to the side of the aquarium using a suction cup.
  • Diffuser: Choose a diffuser to disperse the CO2 into the aquarium water effectively.
  • Scissors: Use scissors to cut the tubing to the desired length.
  • Check valve: Install a check valve in the tubing to prevent water from backflowing into the CO2 system.
  • Sugar: Sugar acts as the carbon source for the yeast in the DIY CO2 generator.
  • Water: Mix water with sugar to create the CO2-generating solution.
  • Yeast: Yeast is the key ingredient that produces CO2 through fermentation.
  • Airstone: Attach an airstone to the end of the tubing inside the bottle to enhance CO2 diffusion.

While the DIY method is suitable for beginners with nano rimless aquariums, it is important to note that for optimal plant growth and health, investing in a pressurized CO2 system may be beneficial in the long run.

Pressurized CO2 setup – the easy step guide

Although the idea of injecting CO2 into your aquarium may seem daunting, the process is actually quite straightforward.

Here is a step-by-step guide to setting up a pressurized CO2 system:

  1. Connect all the components together. Use a spanner to tighten the regulator onto the CO2 tank. Place the diffuser inside the tank, ensuring proper positioning. Connect the diffuser and bubble counter with CO2-resistant tubing. If the solenoid is separate from the regulator, attach it to the regulator.
  2. Once all the parts are connected, proceed to the next phase. Gently open the needle valve on the regulator. This precautionary step ensures that the solenoid is not damaged when the main valve of the CO2 tank is released.
  3. Open the main valve of the CO2 tank to release CO2. If the tank is full, the pressure gauge should indicate a reading of 800-1000 psi.
  4. Slowly turn the needle valve on the regulator to release CO2 into the aquarium. Observe the bubble counter and adjust the rate of CO2 release accordingly.
  5. Adjust the needle valve until you see 1-2 bubbles per second in the bubble counter. Larger aquariums may require a higher bubble rate. Take care when fine-tuning the needle valve, as it can be sensitive.
  6. Monitor the drop checker for a few hours. The color displayed in the drop checker indicates the pH and CO2 levels in the aquarium. Dark blue indicates high pH/low CO2, while yellow indicates low pH/high CO2. Adjust the CO2 needle valve until the liquid in the drop checker turns green. Keep in mind that the drop checker reflects the CO2 level that was present one hour ago, as it takes time to respond to changes.
  7. Set up an electric timer for the solenoid to automatically shut off the CO2 regulator. It is recommended to set the timer to turn on one hour before the lights turn on and turn off one hour before the lights turn off.

Following these steps will help you successfully set up and regulate CO2 injection in your aquarium.

aquario neo co2 diffuser

Balancing Your CO2

It is important to note that overdosing CO2 in your planted tank will not yield better results. Excessive CO2 can lead to oxygen depletion and cause harm or even death to your aquarium inhabitants. Therefore, it is crucial to exercise caution.

Maintaining a consistent concentration of CO2 is key for long-term benefits. The injection rate of CO2 depends on various factors, including the flow rate, surface volume, and number of plants in your tank. Drop checkers are useful tools that can indicate if the tank is deficient or has an excess of dissolved CO2. They provide a safer method of monitoring CO2 levels compared to calculating pH and KH or using other tests, as they offer a smaller margin of error. Regularly observing and monitoring your drop checker will help prevent under or over-dosing of CO2.

betta planted tank

Must-Read Tips

  • To optimize CO2 usage, it is recommended to set the timer to turn off the CO2 infusion 1 hour before the lights are scheduled to go out. This allows for sufficient CO2 to remain in the tank during the final hour of the photoperiod.

  • To ensure an adequate concentration of CO2 at the start of the photoperiod, it is advised to begin the CO2 infusion 1 hour before the lights turn on. This timing is crucial as the initial phase of the photoperiod is the most critical for CO2 availability.

  • Since every tank is unique, it is necessary to test and adjust the bubble counter and schedule multiple times to achieve the desired green color in your drop checker.
  • Before introducing fish into the tank, it is recommended to experiment with CO2 levels. This precautionary measure helps avoid any potential fatalities while fine-tuning your CO2 setup.

  • When observing the drop checker, make sure to aim for a dark green color, distinguishing it from a yellow-green tint.

Make Your aquatic plants happy

Now that you understand the advantages of utilizing CO2 in your planted aquarium, it's time to dive in and give CO2 injection a try! Whether you have a high-tech or low-tech setup, your aquatic plants will thrive and flourish with the addition of CO2. Enjoy the process of decorating your aquarium with vibrant and captivating aquatic plants. Let your creativity shine and create a stunning aquatic landscape.Tell us - Was this article helpful? Please comment your thoughts below!

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