CO2 for Grow Tents and How to Fuel Photosynthesis

Imagine walking into a lush, thriving indoor garden with plants reaching their maximum potential, and the secret ingredient is something as simple yet crucial as carbon dioxide (CO2). CO2 for grow tents plays a vital role in plant growth, and if you’re an indoor gardener, harnessing this powerful gas can take your plants to new heights. Ready to discover the wonders of CO2 supplementation and how it can maximize your plants’ growth and yield? Let’s dive in!

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Key Takeaways

  • CO2 supplementation in grow tents offers increased growth rate, sturdier structure and improved tolerance to high temperatures. This enables you to tap into a greater portion of the Photosynthetic Photon Flux (PPF) emitted by your light source.
  • Various methods for adding CO2 include bags, tanks, generators and DIY solutions.
  • Optimizing CO2 levels during vegetative & flowering stages with efficient grow lights & temperature/humidity management is essential for maximizing plant growth & yield.
  • CO2 can be extremely useful but it is most effective when other growth factors such as light, temperature, and nutrient levels are already optimized.

The Importance of CO2 for Grow Tents

Plants have a natural affinity for carbon dioxide, which is indispensable in the photosynthesis process. In a grow tent, supplementing CO2 can significantly benefit your plants, leading to enhanced growth rates and overall plant health.

Indoor growers are experiencing firsthand the transformative effects of CO2 supplementation in their grow tents. Benefits of boosted CO2 levels are mainly related to improved photosynthesis and include:

  • Sturdier plants
  • Expedited growth
  • Increased tolerance to elevated temperatures
  • Higher success rate with high-intensity grow lights

While elevated CO2 concentrations can lead to increased rates of photosynthesis, termed “CO2 fertilization, the exact growth response can vary depending on the plant species. Studies have shown diminishing returns with extremely high CO2 concentrations. This reinforces the importance of balancing CO2 levels in your garden. 

Source: Kimball, B. A. (1983). Carbon dioxide and agricultural yield: an assemblage and analysis of 430 prior observations. Agronomy Journal, 75(5), 779-788.

Photosynthesis Process

Photosynthesis is the process by which plants intake CO2, water, and light energy to produce glucose and oxygen. Keep in mind that photosynthesis is a complex biochemical process that involves several stages, including the light-dependent reactions and the Calvin cycle. The scientific equation is shown below.

6 CO2 (carbon dioxide) + 6 H2O (water)+ light energy 


1 C6H12O6 (glucose) + 6 O2 (oxygen) 


The resulting oxygen is typically released as a 'waste' byproduct of photosynthesis but a small amount is used during cellular respiration to extract energy from the glucose created. The glucose created is used for many things.

  • Energy: Plants breakdown glucose for energy (ATP, Adenosine Triphosphate) via cellular respiration. ATP is the 'currency' which supports growth, flowering, and making resin.
  • Building: Glucose helps build strong cell walls, leading to strong stems and branches.
  • Special Compounds: Cannabis turns glucose into cannabinoids and terpenes, which protect against pests and attract pollinators.
  • Reproduction: Glucose is essential for making cannabis buds (flowers) and seeds.

CO2 is a fundamental component of photosynthesis. The Calvin cycle, one phase of photosynthesis, uses enzymes to combine CO2 to initiate a sequence of reactions that ultimately produce glucose.

Source: Farquhar, G. D., von Caemmerer, S., & Berry, J. A. (1980). A biochemical model of photosynthetic CO2 assimilation in leaves of C3 species. Planta, 149(1), 78-90.

Enhanced Growth Rates

CO2 supplementation can be a game-changer for your grow tent. Experienced growers have observed that CO2 supplementation can potentially enhance growth rates by up to 20% and size by up to 30%, helping plants produce higher yields. This means you can grow larger, stronger plants and harvest more bountiful crops when you add CO2 to your grow tents.

Increasing CO2 in grow tents has been linked to faster growth, improved yields, and more robust plants. With appropriate CO2 levels, you create an environment conducive to remarkable growth and outstanding outcomes.

Keep in mind that CO2 supplementation is most effective when paired with efficient grow lights and proper temperature and humidity management, ensuring optimal conditions for your plants to thrive.

Methods of Adding CO2 to Grow Tents

Several methods exist to introduce CO2 into grow tents, including:

  • CO2 bags
  • Tanks
  • Generators
  • DIY solutions

Each approach has its advantages and disadvantages, making it necessary to identify the one that best fits your unique space and requirements. Whether you have a small tent or a larger indoor garden, there is a CO2 supplementation method that can help you achieve the desired results for your plants.

Let’s explore some of the most popular methods of adding CO2 to your grow tent and discover the advantages and drawbacks of each option. This will help you make an informed decision and choose the right method for your grow space.

CO2 Bags

Carbon dioxide bags are an easy and affordable option for small grow tents. However, they may lack precise control over CO2 levels. Here’s how they work:

  1. These bags are filled with organic matter that releases CO2 as it decomposes.
  2. Hang the bag in your grow tent.
  3. The bag will provide a steady stream of CO2 for your plants.

While CO2 bags are a cost-effective solution, they might not be the best choice for larger grow rooms or for growers who want more control over their CO2 levels. As always, we recommend monitoring your CO2 levels to ensure levels are adequate.

Summary: CO2 bags are affordable and easy to use, but they offer limited control over CO2 levels.

CO2 Tanks

CO2 tanks offer more control over CO2 levels but can be more expensive and require regular refilling. These tanks are filled with compressed CO2 and can be connected to a regulator to adjust the rate of gas flow into the grow tent. With CO2 tanks, you have the ability to fine-tune the amount of CO2 released, ensuring optimal levels for your plants.

However, the initial investment, ongoing refilling costs, and constant labor of swapping out tanks may be a drawback for some growers.

Summary: CO2 tanks offer precise control over CO2 levels but come with higher costs and the need for regular refilling.

CO2 Generators

CO2 generators are ideal for larger grow operations, providing consistent CO2 levels but may generate heat. These generators typically use liquid propane or natural gas to produce CO2, which is then released into the grow space.

While CO2 generators offer a steady supply of CO2 and are well-suited for larger grow rooms, they may produce heat, which could be an issue if temperature control is already a challenge in your grow space.

Summary: CO2 generators ensure consistent CO2 levels for large grow operations but may raise temperatures in the grow space.

DIY CO2 Solutions

For those who prefer a more hands-on approach, DIY CO2 solutions can be a cost-effective and customizable option for CO2 supplementation. These solutions often involve fermenting sugar and yeast or using other chemical reactions to produce CO2.

While DIY solutions can be tailored to your specific needs and budget, they may require more maintenance and monitoring to ensure consistent CO2 levels for your plants.

Summary: DIY CO2 solutions offer customization and cost-effectiveness but may demand more maintenance and monitoring for consistent CO2 levels.

Optimizing CO2 Levels for Maximum Growth

To fully reap the benefits of CO2 supplementation, you need to optimize CO2 levels during the various growth stages of your plants. The vegetative and flowering stages are crucial periods in a plant’s life cycle, and optimizing CO2 levels during these stages can help you achieve maximum growth and yield.

Correct timing is also a vital aspect of adding CO2 to your grow tent. CO2 should be added during the hours when the lights are on, as this is when plant life is able to use the CO2 for photosynthesis. By carefully managing CO2 levels and timing, you can ensure that your plants make the most of this valuable resource.

Vegetative Stage

During the vegetative stage, CO2 supplementation can accelerate growth and lead to larger plants. This stage is all about building strong, healthy plants that are ready to support an abundance of flowers and fruits during the flowering stage.

Supplementing CO2 during the vegetative stage can give your plants the boost they need to grow bigger, stronger, and more robust, setting the stage for a bountiful harvest.

Flowering Stage

In the flowering stage, CO2 can enhance bud development and overall yield. This is the stage where your plants focus on producing flowers and fruits, and providing them with the right amount of CO2 can result in larger, more potent buds and a higher overall yield.

By optimizing CO2 levels during the flowering stage, you can help your plants reach their full potential and enjoy the fruits of your labor.

Monitoring and Controlling CO2 in Grow Tents

Regular monitoring and control of CO2 levels in grow tents is key to ensuring optimal plant growth. If CO2 levels are too low, your plants may struggle to grow and produce a disappointing harvest. On the other hand, excessively high CO2 levels can be harmful to both plants and humans, with concentrations over 2000ppm being fatal for plants and unsafe for respiration.

Maintaining the right CO2 balance in your grow tent necessitates the use of tools such as:

These tools can help you maintain a healthy grow environment and prevent CO2-related issues. Further optimization especially with a trolmaster system, would be to have your exhaust fan turn off while your CO2 turns on (assuming you have controls in place for monitoring and safety reasons), to avoid just blowing your CO2 out of the tent

CO2 Controllers and Monitors

CO2 controllers and monitors help maintain consistent CO2 levels within your grow space. These devices monitor the concentration of CO2 in the grow tent’s air and shut off any connected CO2 producing devices when the optimal level is achieved.

By using CO2 controllers and monitors, you can ensure that your plants receive the right amount of CO2 for optimal growth, while also avoiding the risks associated with unregulated CO2 levels.

Ventilation and Air Circulation

Proper ventilation and air circulation are essential for maintaining a healthy grow environment and preventing CO2-related issues. A well-designed ventilation system can help regulate temperature, humidity, and CO2 levels, ensuring that your plants have everything they need to thrive.

By combining effective ventilation with CO2 supplementation, you can create a grow tent environment that promotes strong, healthy plant growth and maximizes your harvest.

Potential Drawbacks of CO2 Supplementation

Despite the numerous benefits of CO2 supplementation for your plants, it’s worthwhile to consider potential downsides, including cost implications and safety measures. The initial investment for CO2 supplementation equipment and ongoing expenses for refills can be a concern for some growers. However, the potential benefits of increased growth, stronger plants, and higher yields may outweigh the costs.

When it comes to safety, it’s crucial to take precautions when using CO2 in your grow tent. Unregulated CO2 levels can be hazardous to both plants and humans, so proper ventilation, CO2 monitoring, and adherence to recommended CO2 levels are essential to ensure a safe and productive grow environment.

Cost Considerations

The cost of CO2 supplementation can be a concern for some growers, but the potential benefits may outweigh the expenses. When considering the costs involved in CO2 supplementation, it’s important to weigh the potential increase in growth and yield against the initial investment and ongoing refilling costs.

By carefully evaluating the costs and benefits, you can determine if CO2 supplementation is the right choice for your grow tent.

Safety Precautions

Safety precautions should be taken when using CO2 in grow tents, including proper ventilation and CO2 monitoring. Ensuring that your grow tent has adequate ventilation can help prevent the build-up of dangerous CO2 levels, while CO2 monitors can alert you to any potential issues before they become hazardous.

By taking these precautions, you can create a safe and productive indoor growing environment for both your plants and yourself.

Tips for Success with CO2 Supplementation

To fully leverage the advantages of CO2 supplementation, several key factors should be considered, like using efficient grow lights and controlling temperature and humidity. By optimizing these aspects of your grow tent, you can create the ideal environment for your plants to thrive and make the most of the additional CO2.

Here are some guidelines to ensure successful CO2 supplementation and maximize the potential of your grow tent.

Pairing with Efficient Grow Lights

Using efficient grow lights, such as LEDs, can enhance the benefits of CO2 supplementation and improve overall plant growth. Efficient grow lights provide the right intensity and spectrum of light for plants to optimize their photosynthetic activity, making the most of the additional CO2 provided through supplementation.

By pairing CO2 supplementation with efficient grow lights, you can maximize your plants’ growth potential and enjoy bountiful harvests.

Temperature and Humidity Management

Proper temperature and humidity management are crucial for maximizing the benefits of CO2 supplementation and maintaining a healthy grow environment. By carefully managing temperature and humidity in your grow tent, you can ensure that your plants receive the ideal balance of light, CO2, and other factors for optimal growth.

This can help you create a thriving and productive grow tent, or even a grow room, that yields impressive results.


CO2 supplementation offers a world of benefits for indoor gardeners, from enhanced growth rates to increased yields. By understanding the importance of CO2 for plant growth, exploring various methods of adding CO2 to grow tents, and optimizing CO2 levels during different growth stages, you can unlock your plants’ full potential and enjoy bountiful harvests. With proper monitoring, control, and attention to safety precautions, CO2 supplementation can be a game-changer for your grow tent. 

So, why not give your plants the boost they need and embark on the journey to a thriving, CO2-supplemented indoor garden?

Frequently Asked Questions

Is CO2 worth it in a grow tent?

Adding CO2 to your grow tent can significantly boost plant growth, helping to increase the speed of grow cycles and yield larger harvests. This will work best when conditions such as light and nutrients are optimum, but it can benefit your plants at any stage of the growth cycle, especially during flowering.

How much CO2 do I need for a grow tent?

For optimal plant growth in a grow tent, CO2 levels should be kept between 1200-1500 PPM (parts per million). Monitoring with a CO2 monitor can ensure steady levels throughout the plants' lifecycle.

How do you get CO2 in a grow tent?

CO2 can easily be added to a grow tent by hanging slow-release CO2 bags or bottles, which release a steady amount of CO2 over several days. A rule of thumb is one bag per 4x4 area.

What is the best DIY CO2 for grow tent?

Yeast Fermentation is the best DIY CO2 solution for a grow tent, as it involves using a bucket or vat of yeast to generate extra carbon dioxide.

What are the benefits of CO2 supplementation in grow tents?

CO2 supplementation in grow tents can lead to increased growth rates, higher yields, and healthier plants, which can result in larger harvests.

Author | Chris McDonald

With two decades of expertise, Chris leads Happy Hydro in redefining sustainable gardening and delights in backpacking adventures, mind-expanding journeys, and creating memories with his loved ones.

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