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6 Best CO2 Reactors For Aquariums In 2019 (Reviews & Comparisons)

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Your planted aquarium requires supplemented carbon dioxide for your plants to photosynthesize and filter out harmful toxins efficiently.

Without using one of the best CO2 reactors for aquarium enthusiasts, you run the risk of your plants dying and creating a potentially toxic environment for your fish and invertebrates.

We understand how hard it is to choose the right equipment and ensure you aren’t wasting your money, so we have done the hard work for you.

What Is The Best CO2 Reactor For Aquarium Keepers?

We’ve put together a list of the six best CO2 reactors for aquarium keepers that are available in 2019. Each of the reactors/diffusers listed below are highly-rated with dozens of customer reviews to support your buying decision.

Great Product and costumer service
  • Improves The Health And Growth Of Your Plants
  • Suitable For Tanks Up To 30 To 50 Us Gallons
  • Has Great Size And Nice Design
  • Heavy And Well Made
Prety and functional - excellent quality
  • Its Unique Style Enhance The Beauty Of The Aquarium
  • Suitable For Tanks Below 20 US Gallons
  • Great In Tank And Diffuses Tiny Bubbles
Delivers the CO2 Well - Great Quality
  • Easy To Service / Clean
  • Easy To Install
  • Uniform And Accurate Bubbles
high quality and high performance
  • Excellent And Works Pretty Well
  • Easy To Install And Operate
  • Has High Transparency
  • Simple, Sturdy And Elegant
Neat addition to your tank - Excellent build quality and packaging
  • Improves The Growth And Health To Your Plants
  • Provides Tiny Bubbles That  Easily Disolve In The Tank
Easy to install and very helpful - Use for freshwater or seawater
  • Easy To Set-Up And Works Great
  • Effective And Affordable
  • Attractive, Clean And Modern Looking

1. JARDLI Pollen Glass CO2 Diffuser (JACOP40) - Great Product and Costumer Service


  • improves the health and growth of your plants
  • Suitable for tanks Up to 30 to 50 us gallons
  • has great size and nice design
  • heavy and well made

The JARDLI JACOP40 CO2 Diffuser is a highly-efficient design that provides sufficient atomization of carbon dioxide gas to aid in maximum absorption into your tank. When it comes to JACOP40, you have two different options.

You can choose the smaller 1.5” disc or, the larger 2.0” disc. Smaller tanks in the 20 to 50-gallon range will benefit from the smaller disk, while tanks between 50 to 75-gallons in size can use the larger discs.

The large, flat surface area of the ceramic discs provides for amazing absorption into your water. In our experience, JARDLI produces some of the best-made, highest-quality CO2 reactors for aquarium enthusiasts.

If you’re looking for an inline co2 reactor, the JARDLI JACOP40 could be exactly what you need.

Pro Tip


  • The ceramic disc provides sufficient and efficient gas atomization.
  • You can choose from two different sizes, based on your tank’s needs.
  • Each JARDLI diffuser is built for 20-gallon to 75-gallons in size.
  • The glass body is easy to clean and maintain when needed.


  • The JARDLI JACOP40 does not include a control valve.
  • Glass CO2 reactors for aquariums tend to be fragile. Take care during maintenance.

2. JARDLI U-Shaped Glass CO2 Reactor - pretty and Functional


  • Its unique style enhance the beauty of the aquarium
  • Suitable for tanks Below 20 US gallons
  • great In Tank and Diffuses tiny bubbles

If you’re looking for the best inline co2 diffuser, the JARDLI U-Shaped JACO02A combines both aesthetics with performance to deliver an incredible value for most aquarists. The JACO02A is similar to the JACOP40, sharing a few key features.

Both diffusers are constructed using a U-shaped design that helps add to the visual appeal in your tank while also giving gas time to diffuse adequately. The extended glass U-shaped design allows the diffuser to hang over the side of your tank.

The design of the diffuser means you do not need to use nearly as much tubing because half of the glass is located outside of your aquarium. The smaller 0.8” ceramic disk makes this diffuser great for smaller tanks.

In our opinion, this is the co2 reactor for nano aquarium enthusiasts. It is built to operate in takes smaller than 20-gallons in size, making it great for small planted tanks that are stocked with small schools of fish.

Pro Tip


  • The U-shaped design is incredibly aesthetically, pleasing and functional.
  • The design of this diffuser requires less tubing during installation.
  • The smaller 0.8” ceramic disk efficiently disperses CO2 gas.
  • The design of the reactor makes maintaining and cleaning a breeze.


  • You will need to purchase and tubing separately.
  • The small ceramic disk can be fragile when improperly cared for.

3. Fibst CO2 Aquarium Reactor - delivers The CO2 well


  • easy to service / clean
  • easy to install
  • Uniform And Accurate Bubbles

Coming in at the third spot on our list is the fibst CO2 aquarium reactor. In our experience, this is the best co2 diffuser for large aquarium enthusiasts. The design is exceptionally durable, and aesthetically pleasing with incredible visual appeal while it is installed in your aquarium.

The internal co2 reactor flows carbon dioxide gas through stainless steel tubing until it reaches the small ceramic disc.

You can choose from two different sizes, based on what you need from your system. The 30mm ceramic disk is suitable for larger aquariums, while the 20mm ceramic disc is better for nano aquariums.

Each unit secures the ceramic disk inside of a stainless steel cup. To maintain the system, you will need to open the cup, remove the disc, and clean each thoroughly. The design helps guarantee that CO2 gas does not escape unless exiting through the disc into your tank.

Pro Tip


  • The strong, stainless steel design is incredibly durable and long-lasting.
  • The U-shaped design makes it easy to install into your tank.
  • The stainless steel and ceramic disk are easy to access for maintenance.
  • The included ceramic disk efficiently diffusers carbon dioxide gas.
  • You can choose from two different sizes, based on the size of your tank.


  • The smaller surface area means that less gas gets diffused, overall.
  • You will need to purchase a separate flow control valve.

4. Yagote Glass CO2 Reactor - High Quality And High Performance


  • Excellent and works pretty well
  • easy to install and operate
  • has high transparency
  • Simple, sturdy and elegant

The Yagote line of glass CO2 reactors is some of the most affordable mentions that you’ll see us make. They are designed with budgets in mind, but don’t let the price tag fool you. These are not low-quality products, by any stretch of the imagination.

Each Yagote reactor is constructed using high-quality materials with a strict quality control process to ensure you’re getting the best you can for the price you’re paying. When you see the equipment in action, you’ll be glad you went with Yagote.

Each reactor is constructed from glass with spiral tubing located inside of the outlet. The ceramic disks are best used in 15 to 50-gallon tanks. If you have a larger tank, make sure that you purchase the larger 2.0” disk.

Pro Tip


  • These affordable reactors are incredibly beautifully designed.
  • The internal glass spiral adds an aesthetic appeal to your tank.
  • The ceramic disk diffusers are available in 3 different sizes.
  • The CO2 reactor is easy to install into most tanks.


  • The glass construction can be fragile if cared for improperly.
  • The small ceramic disk sizes may present potential restrictions.

5. jARDLI Music Glass CO2 Diffuser - Neat addition to your tank


  • Improves The growth and health to your plants
  • provides tiny bubbles that  easily disolve in the tank

The JARDLI JACOM50 is one of the best diffusers currently available for large tanks. If you have a tank over 75 gallons in size, this is one of the best diffuser systems that you’re going to be able to find and use.

The design is what sets this reactor apart from its competitors. Each JACOM50 is designed to resemble a small cup where the ceramic disk rests on top. The ceramic discs are designed to create micro-sized CO2 bubbles that efficiently disperse into your water.

The glass tubing rests over the side of your tank with strong suction cups to secure it to the tank’s side glass. Removing the ceramic disk is easy to do and makes it incredibly easy for you to maintain the reactor without worrying about potentially destroying it.

Pro Tip


  • The included 2.0” ceramic disk is designed with large tanks in mind.
  • The ceramic disk provides optimum dispersion of micro-sized CO2 bubbles.
  • The included suction cups provide a secure connection to the side of your tank.


  • You will need to purchase plastic tubing separately.
  • This is one of the more expensive CO2 reactors we’ve featured.

6. atman Enhanced Dissolution CO2 Diffuser - Easy to install and very helpful


  • easy to set-up and works great
  • Effective and affordable
  • attractive, clean and modern looking

Finally, the Atman Enhanced Dissolution CO2 diffuser is one of the highest-rated diffusers for aquariums on our list. Even though we have it listed at number 7, don’t let its placement on our list of recommendations stand in the way of what you’re getting.

The Atman unit is a high-tech piece of equipment. Compared to other CO2 gas diffusers, the Atman diffuser is installed above your tank rather than inside of it. The unit connects to your external filter will helps create carbonized water that eliminates gas loss.

Water passing through your filtration system is injected with carbon dioxide gas before being released back into your tank. That means you will save more carbon dioxide gas while getting complete dispersion from the system.

Pro Tip


  • This is one of the only units to achieve 100% gas dissolution in your tank.
  • The ceramic diffuser cylinder is highly-efficient.
  • The built-in bubble counter helps you accurately measure your system.
  • Each unit comes with multiple strong suction cups for ease of installation.


  • You will need to maintain your filtration system for this diffuser to function correctly.
  • The internal ceramic disk will need to be replaced at least once per year.

How To Buy An Aquarium CO2 Diffuser

Investing in the right equipment for your aquarium can be a hefty upfront cost, but if you understand what you’re looking for, why you need it, and where you can save money, the process becomes significantly more comfortable.

Ensuring that you’re only investing in equipment that meets your specific needs and matches the style of your tank is important for every aquarist. You should also find a reactor/diffuser that matches the size of the tank you’re installing it into.

To make the process easier, there are a few key factors that you’ll want to think about while weighing them against your budget. This will help you decide on whether one reactor is better for your specific needs than another.

Each of the three primary factors you should consider (outside of price) are listed below.
  1. Construction

  2. This is one of the biggest determining factors you should be thinking about. How the reactor is constructed and manufactured determines its quality and how long it will last in your tank.

    Most reactors are constructed from stainless steel or glass. Stainless steel helps your reactor create a mirror-like glow when it is completely submerged into your water. Glass, on the other hand, is more fragile and costs more but gives a more visually appealing appearance.

    Glass tends to blend easier with most aquascapes, while stainless steel will stand out “like a sore thumb” in most cases. Depending on how often you maintain the tank and how often you see yourself removing the reactor, one may be better for you than the other.

    If you’re heavy-handed or are continually moving your aquascape around, a glass reactor may prove to be too fragile. In that case, a stainless steel reactor would be a better choice. However, if you’re looking for the aesthetic appeal, and are careful with your equipment, glass is fantastic.

  3. Convenience

  4. Most of the CO2 reactors you will find today are simple to maintain and take care of. However, some models can be more time-intensive than others. Knowing the difference and what you’re buying can mean the difference between a convenient maintenance process and frustration.

    For instance, co2 reactors that feature internal ceramic disks are, in general, easier to maintain since you’re only required to clean a specific part. Bleaching the discs is easy enough to do, and a thorough rinse is usually all that is needed.

    Other models, though, that will require you to purchase new internal disks and completely replace them can be more difficult. You will need to plan ahead of you are purchasing a reactor that cannot be cleaned. Ordering the disks before you are dealing with problems is critical.

  5. Compatibility

  6. This should be one of the most significant factors you consider (right next to construction materials) when you’re thinking about buying a new diffuser for your tank. Ensuring that the equipment you’re purchasing is compatible with your existing setup is a requirement.

    Each diffuser you consider will be a different size and shape, and able to push an unusual amount of carbon dioxide into your tank. A diffuser that is too small will not provide sufficient CO2 circulation in a large tank. Your fish and plants will feel the effects.

    For larger aquariums, you want to look at diffusers that contain ceramic disks that are larger than 2 inches in diameter. For smaller tanks, smaller disks can be used. In this example, we’re considering a “larger” tank being upwards of 70 gallons, or more, in size.

    Compare the diffusers that you’re thinking about buying to their maximum recommended sizing charts. The manufacturer will let you know the preferred size of the tank that the diffuser is designed to be used inside.

    As a general rule, it’s always better to buy larger than what you’ll think you will need because you can adapt a larger diffuser to a smaller tank. A smaller diffuser cannot be overpowered to deliver enough carbon dioxide into a larger tank.

CO2 Reactor Frequently Asked Questions

Purchasing the right equipment for your tank can feel like a never-ending learning curve.

After years of maintaining tanks and aquascapes, we’ve found out that there is a set of questions nearly every new tank owner goes through or finds themselves asking.

If you’re still having questions about what will work, what won’t work, how to install your equipment, how to care for your diffuser, or make sure you’re not wasting money, each of the questions below can help you out.

How does a CO2 reactor work?

CO2 reactors help add dissolved carbon dioxide into closed systems that can’t produce CO2 gas, or enough CO2, on their own. The reactor (or diffuser) is linked to tubing that allows the CO2 gas to escape.

In some tanks, a bubble counter may be used to help dial in the exact amount of CO2 gas being released into the fish tank. The more giant bubbles are dispersed into smaller bubbles so that the water can absorb the gas more effectively.

The goal for your CO2 reactor is to increase the carbon dioxide levels in your tank.

What are the different styles of aquarium CO2 reactors available?

There are a handful of different styles of CO2 reactors that you can choose from. Each serves a specific purpose, with a particular design. Based on what you need, one may be better for you than another. Or, you could find out you can choose from multiple different styles.

  1. Standard CO2 reactor

    The conventional CO2 reactor is one of the most popular, most common styles you’re going to encounter on your search. These are highly-practical designs, with no frills or extras to get in the way and provide the highest output of carbon dioxide for all tanks.

  2. Glass / Ceramic CO2 Diffuser

    Glass CO2 diffusers are submerged into your tank and secured to the glass or acrylic with magnets or suction cups. Glass / ceramic CO2 diffusers disperse tiny bubbles and are, in general, more affordable than other styles.

  3. Inline CO2 Diffuser

  4. Inline CO2 diffusers are built to attach to canister filters and are most commonly used in large tanks with a high gallon count or a large number of plants and fish. Inline diffusers are easy to use, easy to install, and are known to be incredibly efficient.

    One of the most significant factors that make inline CO2 reactors popular is that they save on the carbon dioxide gas being emitted. They use far less gas because of the method used to inject the gas into the tank. The injection method used allows more time for the gas to dissipate and be absorbed into the water.

  5. Airstone CO2 Diffuser

    Most aquarists will tell you to shy away from airstone diffusers unless you have a particular need for one. Airstones will produce large carbon dioxide gas bubbles that can quickly empty your tank or canister. It’s also harder for your tank to absorb more giant bubbles, so most of the gas gets dissipated into the air instead of the water.

  6. Ladder CO2 Diffuser

    If you’re maintaining a smaller tank, a ladder CO2 diffuser is, in general, going to be the best choice you can make. They’re efficient in their gas delivery and are more affordable than many other styles of diffusers. The ladder-like shape and design are how they get their name.

Why do you need to use a CO2 reactor?

Every aquarium that has fish or plants in it is going to require supplemented carbon dioxide.

Plants require carbon dioxide to properly move through their photosynthesis process. It allows them to create oxygen that your fish can use. The growth of your aquatic plants has a direct impact on the level of oxygen in your fish tank.

Your plants and fish will grow significantly faster when you’re supplementing the amount of CO2 gas they have available. You will also be able to do less maintenance on your tank because your fish and plants keep harmful toxins at lower levels.

What are trusted CO2 reactor brand names?

When you start asking around, most aquarists are going to keep repeating the same brand names over, and over again. Below are a few of the more trusted brands you can purchase from.

  • Yagote Glass CO2 Diffuser
  • Fibst CO2 Reactors For Aquariums
  • JARDLI CO2 Diffusers (Pollen Glass)
  • STARSIDE CO2 Regulators For Aquariums
  • Yagote Stainless Steel CO2 Diffusers

Do I need to use an external bubble counter?

A bubble counter is going to be one of the most critical aspects of your CO2 system. It’s highly advised that you use one inside of your tank. To accurately measure the amount of CO2 gas being released into your tank, you will need a bubble counter.

Your bubble counter works, as the name implies, by counting the number of gas bubbles being released into the tank. If you notice that your tank is measuring high levels of carbon dioxide, you can dial the counter back to release less gas from the canister.

If your tank is measuring low or you see your plants starting to yellow, increasing the number of bubbles being released will help give the plants what they need. Maintaining a specific measurement is nearly impossible to do without a bubble counter.

How do I properly install my CO2 diffuser?

Properly installing your CO2 diffuser into your tank is critical. If you do not take your time, you could end up with leaks or a system that does not function in the right way. Most diffusers will come with in-depth instructions. However, if yours does not, you can use the steps below.

Step 1

Connect your CO2 regulator to your carbon dioxide canister or tank.

Step 2

Connect your solenoid to your CO2 regulator.

Step 3

Connect your solenoid to your bubble counter with the tubing included in your kit. Ensure the tubing connects securely at each end to avoid leaks.

Step 4

Mount your diffuser to the inside of your tank using the included suction cups or magnets, taking care not to crack the glass if you are using magnets.

Step 5

Set the timer on your equipment so it can adequately disperse the carbon dioxide gas through your diffuser.

Step 6

Begin dialling in the needle valve, so it releases the proper amount of gas.

Step 7

Enable your primary valve that allows gas to begin flowing into your tank.

Step 8

Continue gradually opening your needle valve until your bubble counter begins registering tiny bubbles being released into the water.

Step 9

Use a drop checker to measure the amount of gas available in your water.

Step 10

Consider purchasing an electronic timer that will release carbon dioxide gas at precise intervals that you’ve measured based on your bubble counter’s results.

How do I take care of my CO2 reactor?

Your CO2 reactor is easy to care for. If you are using a glass reactor, make sure that you are taking care while handling it to avoid cracking the fragile glass.

When you are ready to clean your reactor, you want to use a water solution mixed with chlorine, allowing your reactor to soak for up to 24 hours. Make sure that you are thoroughly rinsing the reactor before re-installing it back into your tank.

If you need to store the diffuser, you want to ensure that it is kept in a place that is cool and dry.

Keep your equipment out of reach of children to prevent any potential for damage. If you are using a glass diffuser, you want to wrap it in cushion before storing it. It’s also recommended to store the reactor away from other equipment to prevent it from getting banged around and broken.

What is the best CO2 reactor for aquariums in 2019?

Depending on the size of your tank and your specific needs, one of the best CO2 reactors for aquarium enthusiasts in 2019 is the JARDLI JACOP40 diffuser. It gives you multiple options so that you know you’re getting the best equipment for your specific tank setup.

Affiliate links & Images from Amazon Product Advertising API. Last update on 2022-09-11.

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