10 Best Co2 Reactor & Diffuser System

Here’s a fact:

Regardless of your aquatic tank experience, selecting the best CO2 reactor and diffuser system isn’t always easy.

To save time and effort, here are the top 10 best CO2 reactors and diffusers, ranked by customer satisfaction, product rating and overall performance.

10 Best Co2 Reactor & Diffuser System

1. NilocG Aquatics | Intense Atomic Inline CO2 Atomizer Diffuser


This NilocG model is top of the line and top in reviews. As it is an atomizer, it requires a higher than normal psi to push the CO2 through the inline tube. However, this produces a finer mist, allowing for better CO2 dissolution in the water tank. Overall, the higher psi is a good trade-off for more efficient CO2 use.

A bonus to this model is that it comes in two different sizes to accommodate both ½” tubing and 5/8″ tubing.


  • Produces an ultra-fine mist of CO2 with the average bubble size being .1mm
  • It only needs to be cleaned approximately once every 6 months with a simple water/bleach solution.


  • Cannot remove the ceramic cylinder from the plastic in order to clean it thoroughly
  • Requires a higher than normal psi to push the CO2 through the diffuser

2. JARDLI | Pollen Glass CO2 Diffuser


This delicate CO2 diffuser from JARDLI is a beautiful product. It comes in two different tubing sizes (1.5″ or 2″) to accommodate tanks either 50 gallons or 75, respectively. It is important to note that one of the few things customer reviews cautioned is that the glass tubing is incredibly fragile and must be handled with utmost care. Despite this small ‘flaw’, this model makes the Amazon’s Choice list and is designed for optimal CO2 flow.


  • An ‘Amazon’s Choice’ product for product reliability, customer satisfaction, and overall performance
  • Comes in two sizes (1.5″ or 2″) for 50 gallon tanks or 75
  • The U shape design is intended to prevent blockage of CO2 flow


  • The required tubing is not included with the product and has to be purchased separately before this can be installed
  • It is recommended that the tube should be cleaned once every two weeks (approx.)
  • Stops working under low pressure if tubes are not cleaned well

3. JARDLI | Glass Inline CO2 Atomizer Diffuser


This next JARDLI model is another beautiful glass atomizer diffuser. The inline mounting reduces the amount of algae growth in the tank and tubing which leads to a nice, low maintenance piece. As a whole, this diffuser is a nice solid little piece of glass and much less likely to break than many of its counterparts. The reviews regarding the diffusion as a whole are positive and the microbubbles come out nicely.


  • Inline mounting reduces photosynthetic algae growth which keeps the tank and water cleaner
  • JARDLI customer service is highly recommended and very fast and courteous if the product has issues and/or a replacement is needed
  • The glass is well made and solid; it doesn’t break as easily as some of the competing products


  • The connecting tube for this piece is fairly short and may require zip ties or other connectors to keep it together

4. Sera Flore | Active CO2 Reactor


This Sera Flore reactor is a great buy. The product is made with a nice quality acrylic and works for tanks that hold up to 160 US gallons. The unit is just 3″ long and can produce 500-1000 bubbles per minute depending on the model. Additionally, it can be mounted inside or outside of the tank. Customer reviews acknowledge the good bubble breakup and overall quality as a whole. The only downside is that the union nuts included for the hose don’t seem to work much at all. It is recommended that hose clamps are purchased and used instead.


  • Produces 500-1000 bubbles/min depending on the model
  • Can be mounted inside of the tank or outside without disrupting the performance
  • So long as it is plumbed correctly, the noise level is relatively unnoticeable


  • Hose union nuts that are included are basically worthless & it is recommended you purchase hose clamps instead

5. ISTA 80076 | CO2 External Reactor


This ISTA product is one of the best reactors on the list. Despite needing some DIY tweaking to get up and running properly, it actually has the best performance overall. The main cautions in the customer reviews are not related to the product performance. Rather, the clips and fittings that are included with the reactor are not sized correctly. However, once these have been replaced (and a few reviewers even cemented the tubing in a few spots) the reactor operated at peak performance and had a nice long lifespan. The reactor requires a lower flow rate and runs smoothly and quietly.


  • The product runs great and has a lifespan of several years (or more)


  • Fittings for water intake & return aren’t correctly sized which causes leaks
  • The tubing clips are not the correct size for the standard tubes and are recommended to be replaced before installation

6. Rhinox Nano | CO2 Diffuser


This Nano CO2 diffuse from Rhinox has one of the best designs for controlled, slow release of CO2 into a tank. It is designed to work for tanks up to 20 gallons and the shape allows for slower water speed which aids in the overall CO2 diffusion. A few customer reviews did caution, however, that the glass tubing is incredibly fragile and the unit had a tendency to turn off at random.


  • The product is designed with an extra-fine porous ceramic micro bubble diffuser plate for optimum diffusion
  • Cylindrical shape slows down water speed which allows for a more controlled CO2 diffusion
  • Assembly and installation are both quick and easy compared to other models


  • The glass tubing is incredibly fragile & is easier to break than other comparable models
  • The diffuser is noticeably noisier than other models & doesn’t diffuse CO2 at a consistent rate

7. JARDLI | Glass CO2 Diffuser


Another beautiful glass diffuser from JARDLI makes the list. This model is built to work for tanks up to 20 gallons and is almost 8″ long. The length is a nice feature of this model as it allows for a higher surface area to tank volume ratio. This allows for a fuller, CO2 diffusion into the tank, rather than limiting it to a small, little circle radius.

Overall the reviews of this model were positive. For best results, it is recommended that you soften the silicon or rubber tubing prior to inserting it into the diffuser. Just 30 seconds in boiling water is enough to reduce the risk of breaking the tubing upon insert.


  • There is a high surface area to volume ratio which allows for optimum CO2 diffusion


  • It is recommended that you soften the silicon or rubber tubing by sitting in boiling water for 30 seconds before inserting it into the diffuser

8. Segarty | Glass CO2 Diffuser


Segarty has done it again with a high-quality glass and ceramic diffuser for your aquarium. It works for smaller tanks up to 50 gallons and comes with the diffuser and u-shaped tube. The customer reviews do not caution against fragile glass as much as competing products and to ensure even the glass lasts even longer, it is recommended that the glass tubing is wet prior to the tubes being inserted. The only caution with this product is that the bubbles are not consistently sized, but that doesn’t impact the overall performance as a whole.



  • The large ceramic membrane allows for a highly efficient distribution of CO2


  • Bubbles are not sized consistently even though the surface area is quite spacious
  • This unit can only be installed in a corner of the tank due to the positioning of the suction cups

9. ISTA Turbo | CO2 Reactor


This CO2 reactor from ISTA is compact. It is intended for external use and sits about 10in tall. Installation is nice and simple and it does not require an electric connection; it runs off of the water flow generated by the tank filter.

According to customer reviews, there are no issues with the quality of this piece. However, there are cautions that the performance is inconsistent. Depending on the tank filter, the water flow is different and impacts the reactors’ overall reliability. Additionally, the product does not come with the necessary tubing.


  • The product is compact & requires only simple installation before being ready to use
  • Doesn’t require electricity to run because it uses the water flow from the tank filter


  • Flowrate required for this to work is not consistent across canister filters
  • Inconsistent reactor performance overall according to the customer reviews

10. Rhinox Spio III | Diffuser and Glass Reactor


This Rhinox Spio is a tiny little beast for your tank. It is not even 2″ tall, but it can pump out enough CO2 for a tank up to 20 US gallons. While the title reads it as a reactor, it is actually a diffuser. Customer reviews speak to the overall high quality of the glass reactor as well as the micro bubbles that are produced. This diffuser runs well and gets the job done while also bringing a nice visual element to the tank.

It is recommended that the product is soaked in water for at least half an hour before it is installed and that the glass tubing gets wet before any silicon or rubber tubes are inserted to avoid damaging the unit.


  • Slow CO2 release rate allows for nearly 100% diffusion into the tank
  • For optimal CO2 release it is recommended for pressurized CO2 tanks
  • Design of the internal glass swirl in the diffuser is aesthetically pleasing and complements tanks


  • Does not work well with homemade CO2 products and diffuses these with mixed results


What is the difference between a reactor and a diffuser?

A diffuser takes pressurized CO2 gas and pushes it through the tube to a ceramic plate where the gas is forced through tiny holes that break up the CO2 and release it into the tank.

A reactor mixes tank water and CO2 in a separate area (inside the reactor) and then releases the CO2 rich water back into the tank.

What is an atomizer diffuser?

An atomizer diffuser force CO2 through the ceramic plate, but the holes tend to be much smaller so that the bubbles of CO2 are ultra-fine. This requires more pressure to force the gas through the smaller holes, but it results in a higher CO2 dissolution rate.

Which is more efficient – a reactor or diffuser?

There are two different schools of thought on this. Generally, most feedback is that reactors are more efficient and infuse more CO2 into the tank than the diffusers because any bubbles that leave the diffuser plate ‘waste’ CO2 because they float to the top instead of dissolving into the water. However, reactors don’t always function reliably when it comes to infusing CO2 with tank water and are more expensive, so diffusers are highly recommended as less-expensive alternatives.

Why does my tank need extra CO2?

If you are looking to grow aquatic plants you will need to provide them with extra CO2 for optimum growth. It keeps them healthy and fresh-looking which improves the visual appeal of your tank.

What are the additional items I might need?

Not all reactors or diffusers come with the required tubing. You may also need additional clamps, suction cups, and CO2 canisters/sources in order for your unit to work.

Will the diffuser/reactor work with my tank?

Diffusers and reactors are not tank-specific. The only thing to keep in mind is the overall size of your tank. Most units will only work up to a certain gallon size so for top performance it is best to adhere to what the manufacturer recommends.

Do I need to clean my unit?

Yes, all units do need to be cleaned. It is a relatively simple, but sometimes timely, process that generally requires boiling water and/or water: bleach solution. The ceramic plate for diffusers is generally soaked in hot water in order to clean out the tiny holes and the reactor tubing can be flushed out to prevent build up.

How often will I need to clean my unit?

It depends on your unit. Manufacturers – along with good customer reviews – will have a recommended cleaning timeframe. Less-efficient units may need to be cleaned weekly, while some can run for 6 months before they will require cleaning.

You’ll know when it’s time to clean your unit if you start to see a buildup in the tubes (for reactors) or when the ceramic plate seems murky or the bubble production decreases (for diffusers).

What is the difference between internal and external mounting?

Internal mounting is when the unit is placed inside the tank. All diffusers are put inside the tank because of the way they diffuse CO2. Reactors are generally external, but a few models can also be immersed in the tank as well.

It is important to consider your tank and what you already have inside to ensure you have space if you choose an internally mounted unit. If the tank space is limited, you may want to consider an external reactor instead.

Are reactors noisy?

For the most part no. It is product-specific so some of the reactors generate more noise than others, but overall if the unit is set up properly there will be minimal noise. It is best to check customer reviews to get a decent gauge on how loud the unit may be.

What do I do is my unit starts to leak?

Some of the lower-quality units will leak where the tubes connect. An easy DIY fix is generally to replace the connectors with nice hose-clamps and/or some quick cement. If the unit is leaking terribly that may be a sign that it needs to be replaced.

What air pressure do I need for my diffuser?

This will vary depending on the unit that you have. Most diffusers run off of the water from the tank filter which varies. The pressure can run anywhere from 30 – 50 psi. You will have to monitor the unit performance when you first install it and adjust as needed. The pressure will also vary depending on whether you have an atomizer diffuser (which requires higher pressure) or a standard diffuser.

How do I attach it to my tank?

The most common way to attach diffusers and internal reactors are suction cups. Most units will come with one or two and it is recommended to purchase additional ones from a pet store that may support the unit better. Diffusers are all quite light so the suction cups do the trick.

Externally mounted reactors are generally attached with suction cups as well or hooked to the side of the tank.

Why does my glass piece keep breaking?

Most diffusers are quite fragile since the glass is thin and small. The same goes for the tube inside of reactors. It is recommended that you be cautious when handling your glass pieces and many units recommend soaking the silicon or rubber tubing prior to inserting it into a reactor or connecting it to a diffuser in order to prevent breakage.

Can I prevent algae build up?

Regular cleaning per the unit instructions will keep algae build-up at a minimum.

Do I need a reactor or diffuser that is nano- tank specific?

Nano tanks are generally tanks that are 10 US gallons or smaller. Most diffusers and reactors have a gallon limit, but not a minimum so you don’t need to look for a unit that is Nano-tank specific. Slight adjustments might have to be made to the flow since smaller tanks don’t require as much CO2, but that is all that would need to change.

Can I use a DIY yeast CO2 mixture?

Diffusers and reactors will generally have a note from the manufacturer letting you know if the unit is compatible with homemade CO2 mixtures. It is also good to check the customer reviews and/or question section as there are often times the manufacturer will caution against the use of DIY mixtures, but the reviews will attest that they work just fine.

Do I need to invest in a bubble counter?

A bubble counter is a highly recommended feature in order to ensure the unit functions at top performance. However, it’s not a required piece in order for a unit to run.

What do I do if my bubbles seem too large or inconsistent?

If the CO2 bubbles are inconsistent or are large and floating to the top (for diffusers), it may be time to clean the plate. Additionally, you may want to try adjusting the water pressure and see if it’s too low to properly force the gas through the holes on the plate.

The bubbles stopped coming out of my diffuser – what do I do?

Time for a cleaning and a checkup! Check the water flow and pressure to ensure that nothing is blocking the CO2 from making it to the plate. You can also check to make sure the CO2 source has not been depleted. If all else fails, it may be time to invest in a new unit.



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