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The Best CO2 Reactors for 2022

best co2 reactor

Unlike a diffuser, a CO2 reactor guarantees that most of the carbon dioxide from your tank dissolves into the water. This happens because the reaction chamber ensures that the carbon dioxide molecules are in contact with the water long enough for them to dissolve.

Carbon dioxide diffusers do a somewhat effective job, but they don’t have nearly the same efficiency as the best CO2 reactor. Diffusers rely on a ceramic disc or a finely perforated membrane to produce ultra-fine bubbles that will help disperse the CO2 in the water. However, there are usually still a lot of bubbles that break at the surface.

When you use an aquarium CO2 reactor, you will not even see the bubbles in the water. The reason is that the gases have already dissolved in the water right inside the reactor. Aside from a couple of bubbles that make it out, the reactor dissolves 100% of the CO2. This means you will be getting your money’s worth on your CO2 tank.

This article will teach you all about carbon dioxide reactors. It will also show you a couple of recommendations.


Best CO2 Reactor Reviews

1. Sera Flore Active CO2 Reactor

sera flore active co2 reactor

If you have a large planted tank, something along the lines of 100+ gallon capacity, then you will want to use the aqua medic co2 reactor 1000. This device is one of the most efficient reactors that I have tested so far.

I noticed that it can dissolve up to 1000 CO2 microbubbles in a minute, which is plenty for a 100-gallon tank. On the other hand, if you have a small aquarium or do not have that many plants, you can dial the pressure down.

Unlike CO2 diffusers, this CO2 reactor aquarium is constructed from tough and durable acrylic. You can drop this on the floor and it would not even get a scratch. This means that maintenance and cleaning are much easier. Whenever I need to clean my CO2 reactor, I do not need to hold it like it would break apart at any time.

Moreover, because it is not as fragile as glass diffusers, installation is not quite as nerve-wracking. I liked how I was able to connect the rubber hoses to the device without worrying about snapping the connector or accidentally crushing the device and having to pull shards of glass from my hands.

Speaking of installation, you can position the Sera 2 reactor inside or outside your fish tank. If your tank is big enough you can choose to hide this reactor behind the plants. I chose to install mine outside the tank so I can monitor its condition easier. Also, it looks kind of cool, making it a good conversation starter when I have non-aquarist guests.

I do not have any issues with this CO2 reactor but there are a couple of reviews that I stumbled upon that were not so positive. The reviewers all said that the impellers in their reactors made a lot of noise. This has not been an issue with me, but it might be because mine came from a good batch.

  • Dissolves up to 1000 CO2 bubbles per minute
  • Made of high-quality acrylic
  • Easy to install and maintain
  • Allows installation inside or outside the tank
  • Ideal for use in large tanks
  • The impeller can be quite loud

If you have a large planted tank, you should get this device as it will help you keep your hydrophytes healthy and happy. On the other hand, if you have a tank that is under 50 gallons in capacity, then it is overkill.

2. ISTA Co2 Planted Aquarium Reactor

ista co2 planted aquarium reactor

This CO2 reactor for a planted aquarium is a good choice if you have a small tank. This reactor has a small and compact design that is ideal for small tanks, like 10- to 15-gallon capacity ones.

Aside from being small, this device does not also require extra tubing. You just need to place this in your tank. Plug in the hose from your carbon dioxide tank and turn on the device.

Installation is also a breeze as you do not have to connect anything else to the device other than the output hose of your carbon dioxide system. Once you attach the rubber hose, the only thing left to do is stick this submersible device inside the tank using the strong built-in suction cups at the bottom of the device. You should then plug it in.

The Ista turbo CO2 reactor is primarily a surface film skimmer. This means it removes the oily film that tends to form on the surface of the water in an aquarium. Not only is that substance disgusting, but it also affects the overall health of the tank. In addition to being a surface skimmer, this device can also work as a makeshift water filter.

Don’t be fooled by its small size. This device has a rather powerful submersible motor. This tiny thing is capable of displacing up to 100 gallons of water per hour. This is the reason why if you will be using this device as a filter, it can clog up quickly with accumulated debris from the water.

As neat as this device is, I do have a huge issue with it and it is about its carbon dioxide diffusing capability. Although the product states that you can use the device as a CO2 diffuser, its efficiency pales in comparison to the performance of the cheapest diffusers in the market.

For one thing, the bubbles that this device produces are so big compared to the misting that most diffusers can provide.

  • Small and compact design
  • Easy to install – The suction pads hold on tightly
  • Can also work as a water filter
  • Effectively cleans the surface of the water
  • Can also diffuse CO2
  • Not that great when it comes to CO2 diffusion

I don’t have any complaints when it comes to this product’s surface skimming capabilities, but as a CO2 diffuser, it is quite disappointing. If you are buying this because you want a compact yet effective surface skimmer, then you would like this product. If you are looking for a good CO2 reactor, then this product is not it.

3. Avanti Refillable Cartridge Housing Reactor

avanti refillable cartridge housing reactor

If you are using a reverse osmosis filter for your aquarium water, you need to check out this product. This is a refillable filter cartridge. With just that, you already know that you will be saving quite a lot of money. This will save you from all the trouble changing disposable filters every month or so.

The beauty of using this refillable filter cartridge is that you can choose your filter media, which also adds to your savings. You can choose to buy filter media in bulk to save on costs. You can also experiment with different combinations of filter media to figure out which works best.

Also, unlike most of the disposable filter cartridges, this one is see-through. It will let you check the condition of the filter media without having to open the container. Disposable cartridges are not clear, so you can only follow the recommendation of the manufacturer on when you should replace it, even if it is still usable.

With this product, you can truly capitalize on the money you spend on filtration. You do not even have to worry if this product will fit your system as this follows the standard measurements used by many filter companies. If you are using a commercially available RO filter system, you can be sure that this refillable cartridge will fit.

Can you use this filter cartridge as a makeshift CO2 reactor, though? Yes, you can. If you have the know-how (there are plenty of online tutorials if you don’t), you will be able to jerry-rig this cartridge and turn it into a carbon dioxide reactor.

However, this is only viable if you are using a DIY carbon dioxide supply. If you are using a tank, it would be better and more cost-effective to buy an actual CO2 reactor.

  • Cheaper and more economical alternative to disposable filter cartridges
  • Allows you to choose your reactor media
  • Features a clear acrylic housing that lets you see the condition of the filter media
  • Highly durable and longer-lasting compared to disposables
  • Can fit inside most RO systems
  • This is not a CO2 reactor but it can be jerry-rigged to become one

If you are handy enough, you can jerry-rig this cartridge for use as a makeshift, low-pressure CO2 diffuser. This means if you are using a DIY CO2 setup, you can use it as your diffuser.

4. ISTA 80076 Co2 External Reactor

ista 80076 co2 external reactor

This device provides the best reason why you should buy a carbon dioxide reactor – that is it can dissolve 100% of the carbon dioxide gas into the water. This means you do not need to have your tank open quite as long as you would if you used a regular diffuser. That said, monitor the water conditions to ensure that the water is not oversaturated.

Because this CO2 reactor is so efficient at its job, you can use it on large-capacity tanks with no problem. I have this one hooked up to a 150-gallon tank and despite its size, it had no issues keeping the CO2 saturation of the water at an ideal level. I only need to leave the tank on for two to three hours a day.

One of the best things about this product is that it made use of clear yet durable acrylic material. There have already been several instances where I had to go to the emergency room to have small shards of glass pulled out of my hands because I held glass reactors the wrong way. This one is so tough that I might not break it even if I wanted to.

It is also easy to install compared to the other reactors I have tried in the past. Just connect the return hose of the filter system and the airline coming from the CO2 tank. Ensure that you connect them the right way, though, and it will be ready to use.

You can also choose to mount this on the side of your tank or have it hidden inside your aquarium cabinet for a clean look.

The only issue that I have with this product is that the “hose clamps” that come with the device absolutely do nothing to hold rubber tubing in place. I had to remove the clamps from the reactor and get real hose clamps from the hardware store because the hoses kept slipping off the connectors.

  • Works well and dissolves near 100% of CO2
  • Can work for large capacity tanks
  • Made of durable acrylic
  • Easy to install
  • Looks interesting enough to mount outside the tank cabinet
  • The “hose clamps” do nothing

After you manage to find working replacements for the hose clamps, this diffuser will work quite well. It may not be the best out there but it is certainly not the worst. For the price, you cannot complain that much.

5. Awesome Aquatic Inline CO2 Reactor

awesome aquatic inline co2 reactor

This inline CO2 reactor is so compact that no one would even notice it even when you leave it out in the open for them to see. You might even forget where you placed it after a couple of months have passed. However, even though this is quite small, it does a good job of dissolving carbon dioxide into the water.

I am not a fan of the blown glass diffusers and reactors because they are so fragile. This is why I liked this CO2 diffuser/reactor. This product is made from stainless steel and durable acrylic.

Even if you throw this device against the wall, you will hardly make a mark on it. This makes handling, installing, and maintaining this device not among the most nerve-wracking affairs.

Another nice feature of this CO2 reactor is that it has a built-in check valve. This means that it will only let fluids pass through one way but not back the other way. This means if you are running low on CO2, there is no chance that water will be getting into the air-line and the CO2 tank. It is a neat feature because that would be an expensive fix.

Unlike other CO2 reactors, this one disassembles completely for easier and more thorough cleaning. This will also allow you to change the ceramic diffuser if you think that it needs replacing. I feel that it is much better than just soaking the entire thing in a bleach solution.

The small size is also the cause of a serious issue. Because the reactor is small, pressure builds up rather quickly inside it, which often causes the rubber hose to slide off the connector. This means that you will need to get tiny hose clamps to keep the air-line and the ones coming from the filter from popping off the device.

  • Compact design
  • Made using durable stainless-steel and acrylic
  • Comes with a built-in check valve
  • The inline mount makes it low-maintenance
  • Disassembles for easy cleaning
  • You will need strong hose clamps to prevent leaks

Don’t get me wrong, this product works but it requires quite a bit of tinkering to get it to work efficiently. For its price, you can just compromise and tinker with the installation to make it work and save a couple of bucks.

What to Look For When Buying a CO2 Reactor

aquarium co2 reactors

Not only will you be wasting your money if you bought the wrong CO2 reactor, but you will also be killing all the plants that you painstakingly planted inside your tank. Here are some features and qualities you need to keep an eye out for when shopping.

Ease of Installation

You will be the one installing the device on your aquarium, so it should at least be easy enough to install that you can do it by yourself. Fortunately, most carbon dioxide reactors in the market rarely have complicated installation procedures. Most of them only require you to stick the right hose into the right connector.


You can tell how efficient a CO2 diffuser is by how many bubbles you see coming out from it and the correct answer here is zero. If it seems like nothing is happening, you know that your reactor is doing a fantastic job of infusing the water with carbon dioxide. It is when you see large carbon dioxide bubbles that should worry you.

Since there is no way that you can test out a product before you purchase one. The only options you have left are to rely on customer reviews or join an online forum and ask the members about their opinions regarding a specific brand or model of CO2 reactors.


One of the advantages of CO2 reactors over most of the diffusers that you have in the market is that the reactors are usually more durable and made of tougher materials. This means you have more material options other than fragile glass. If you want a CO2 reactor that lasts for years, get one made from ultra-clear acrylic.

On the other hand, acrylic gets dull over the years while glass does not. If you want the look and feel of glass, you can try devices made of resin glass. This is much more durable than regular glass but it is still not as sturdy as acrylic.


This factor will be purely subjective as not all people have the same attitude when it comes to the prices of items. You will be the one who should determine if a certain brand of CO2 reactor is beyond your financial capabilities.

If you don’t have the budget for it, you should just look for another one that fits your budget. Keep in mind that just because one CO2 reactor is more expensive than the next one, it does not automatically mean that it is better.


Keeping a planted aquarium is hard enough as it is, so you should find ways to make it less of a hassle. That said, find a CO2 reactor that is easy to clean and maintain.

Inline or submerged?

This will be purely a matter of preference. If you have a large tank, then it will probably be fine to install the reactor inside the tank. On the other hand, if you are looking to give your aquarium a clean and minimalist look, you can just install it in line with the filter system.

Frequently Asked Questions

co2 reactor for planted aquarium

How to Install a CO2 Reactor?

Almost all CO2 reactors need to be installed in line with the water filter pump, typically on the outlet line. This means you need to cut the outlet tube and install the diffuser between the cut line. Once you install the water-line, you then need to install the hose coming from the CO2 tank.

When you turn on the water pump and the CO2 tank, water would fill the chamber, which would then make the impellers turn. The agitation will enable the CO2 to dissolve better into the water.

Is a CO2 Reactor Better than the Diffuser?

When efficiency is concerned, the answer would be a yes. Reactors are better than diffusers when it comes down to carbon dioxide dissolution. However, because there are moving parts and a somewhat tricky installation process, some people would rather choose the simpler to use and easier to install CO2 diffusers.


If you have a large planted aquarium, instead of using several CO2 diffusers, you should just get one highly efficient CO2 reactor. The best CO2 reactor will have no problem whatsoever infusing a large volume of water with ample carbon dioxide to keep live water plants healthy and thriving.

However, not all CO2 reactors are made the same. This is why you need to learn how to discern a good device from one that just does a so-so job. Keep in mind that a suitable CO2 reactor will be the key to having a healthy and beautiful planted aquarium.

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