Getting enough CO2 in a planted aquarium is a vital part of having a thriving aquatic environment. We’ve put together a list of the best aquarium CO2 diffuser to help you choose the right one for your tank.
To have a live, densely-planted freshwater aquarium, you need to fertilize your plants with carbon. Carbon is not easily replenished in liquid or solid form like other fertilizers and is generally supplied as gas. To mix carbon dioxide gas into your aquarium water, you need an efficient aquarium CO2 diffuser.
Comparison Table
Top Top Top | Pm0606 Micro co2 Bubble Diffuser air Stone Built in Bubble Counter, Smallest Smooth co2 Bubbles, Very Good for Aqua Plants, Shrimps (co2 Diffuser for Large Size Tank) 1" inch | Prime | AMAZON | |
 Top Top | JARDLI Pollen Glass CO2 Diffuser with Bubble Counter for Aquarium Planted Tank | PrimeEligible | AMAZON | |
 Top Top | fibst CO2 Diffuser for Aquarium, Excellent CO2 Solubility Ensuring Vigorous Plants (30Dx350L) | PrimeEligible | AMAZON | |
 Top | JARDLI Music Glass CO2 Diffuser for Aquarium Plant (2'' for Tank Beyond 75 gallons) | PrimeEligible | AMAZON | |
 Top | Zerone Co2 Diffuser, Stainless Steel Carbon Dioxide Diffuser Fish Tank Supplies Aquarium Equipment(L (300mm)) | PrimeEligible | AMAZON | |
 Top | Mumusuki -Shaped CO2 Diffuser 4 in 1 DIY CO2 SUystem Valve Bubble Counter Planted Aquarium Carbon Dioxide Reactor with Check Valve Glass Pipe Sucker | Prime | AMAZON | |
 Top | Fluval Ceramic CO2 Diffuser for Planted Aquariums, A7548 | Prime | AMAZON | |
 Top | Aquario Neo Co2 Diffuser New Version Special Large (40+ gallons), Authentic Product, Made in Korea, Clear | PrimeEligible | AMAZON | |
 Top | Sera Flore Active CO2 Reactor 500 - Small 66-160 Gal | Prime | AMAZON |
They are designed to add the right amount of CO2 quickly and easily and are generally inexpensive and easy to install.
Top 10 Best Aquarium co2 Diffusers for Your Aquariums
Best Aquarium CO2 Diffuser Reviews
1. Pm0606 Micro CO2 Bubble Diffuser
The Pmo606 Micro Co2 Bubble Diffuser is a good choice if you are looking for something that produces micro-fine bubbles, which help disperse CO2 quickly, making it readily available to your plants.
This diffuser is made of sturdy glass that does not break easily. It’s washable and can be used over and over again without having to replace it.
Part of the reason this diffuser is so effective is because it is so light and airy, the reason it can produce so many fine bubbles. It is cup-shaped and has a large surface ceramic disc for greater effectiveness.
Benefits
- Produces micro bubbles
- Sturdy glass
Cons
- None that we can see
2. JARDLI Pollen Glass CO2 Diffuser with Bubble Counter
The JARDLI Pollen Glass CO2 diffuser is a great choice if you are looking for an aesthetic match to your aquarium. It creates little bubbles that look lavish in your display tank, while giving your plants an easy way to absorb what they need to grow. The ceramic membrane has a large surface area and is therefore able to create so many bubbles.
This is a small diffuser, only 0.8 inches, and is designed for use in tanks under 20 gallons. It is compatible with 4/6mm CO2 tubes and is made of high quality materials like glass and ceramics.
To make sure everything is working properly, wet the glass tube before attempting to connect any tubes. This acts as a lubricant and the tube slides without risk of damage.
It’s also important to ensure that the ceramic disc, tube and other surfaces are soaked for at least 30 minutes before use.
Benefit
- Large bubble production
- Aesthetic look
Cons
- Only designed for tanks under 20 gallons
3. fibst CO2 Diffuser for Aquarium
The Fibst co2 diffuser is a little different from the others we tested as it is made of stainless steel instead of glass. Stainless steel does not rust or corrode and can last a long time in your aquarium.
It also adds a simple and elegant piece of art to the environment. Produces fine, round bubbles as opposed to partial bubbles created by other diffusers.
Cleaning is easy, just turn the stainless steel mug to remove the ceramic blade cover. Installation is also a breeze, just hook the diffuser over the edge of the tank and use the stainless steel fitting to secure it.
Another great thing about this one is that it comes with a pretty impressive warranty. You get 6 months for the ceramic plate and 24 months for the other parts.
Benefit
- Stainless steel make
- Simple and elegant
- Easy installation
- 6-24 month warranty
Cons
- None that we can see
4. JARDLI Music Glass CO2 Diffuser for Aquarium Plant
The JARDLI music glass CO2 diffuser is designed for large tanks of 75 gallons or more. The unique, artistic look isn’t obtrusive and doesn’t detract from the aesthetic of the tank, yet still adds a bit of movement and visual appeal.
The large 2-inch diameter and ceramic membrane create a broad mist of tiny CO2 bubbles. This is very important because it is much easier for the smaller bubbles to diffuse into the water, making the CO2 usable for your plants.
It comes with two suction cups for easy installation and the diffuser itself is made of high quality borosilicate glass which is very strong and durable. The construction is excellent and makes a great addition to any large plant aquarium.
Benefit
- Unique visual appeal
- Creates small bubbles
- Strong, durable glass
Cons
- None that we can see
5. STARSIDE Aquarium CO2 Diffuser
Made of high quality material, the STARSIDE aquarium CO2 diffuser features a U-shaped design to match any countertop. Because it is made of resin and not glass, it is more resistant to bending and extremely durable.
It uses a ceramic disc that produces a steady stream of tiny bubbles that easily diffuse into the water to benefit your plants. Installation is also easy, simply using the suction cup to attach it to the side of the exhaust and adjust the U-bend as needed.
One of the best things about this design is that it’s very understated. The U-shaped section fits easily over the side of most rimless tanks and some tanks that also have a rim. If the U-shaped part does not fit, the rest of the diffuser still works with a simple tube.
Benefit
- Resin, U-shaped design
- Durable and adaptable
- Easy installation
Con
- None that we can see
6. Yosoo U-Shape DIY CO2 Diffuser
Yosoo’s U-shaped DIY CO2 diffuser is easy to install and operate. Use the included suction cup to attach it to the side of your tank and connect it to your CO2 source. The small see-through design is easy to hide so it won’t distract from your tank setup.
This diffuser is multifunctional. Not only is it an atomizer, but it also acts as a check valve, bubble counter and U-shaped air inlet. The U-shaped gasket makes it very easy to set up the tube and the bubble counter works well with accuracy.
The check valve is always handy and the aerator produces bubbles of the correct size for diffusion. This is a simple design that is highly effective and ideal for small to medium sized aquariums.
Benefit
- Small and inconspicuous
- Multifunctional
Cons
- None that we can see
7. Hagen Fluval Ceramic CO2 Diffuser
The Hagen Fluval Ceramic Co2 Diffuser has a round plastic housing around a ceramic disc. It looks like a little black donut or tire. A small nipple protrudes from the top of the donut to which the CO2 pipe connects.
Everything can be attached to the side of the tank with a suction cup, leaving installation and use super simple.
It’s nice that this diffuser is easy to install and doesn’t break easily, but if we’re honest it doesn’t have an appeal visually. Most diffusers look great, but this one looks like an odd piece of plastic in the tank.
Benefit
- Simple installation and use
- Durable
Cons
- No aesthetic appeal
8. Aquario Neo CO2 Diffuser L
The Aquario Neo CO2 diffuser is a unique addition to this list because it is the only diffuser that works with a do-it-yourself system. The membrane is so porous that it will bubble even at low pressure.
The diffuser housing is made of clear acrylic which is much more resistant to breakage than glass. The folks at Buce Plant even threw the diffuser on the floor and it still didn’t break.
Since there have been reviews of people complaining that their glass diffuser broke after a 6-inch drop, this is a huge advantage.
Benefit
- Sturdy acrylic material that won’t break easily
- DIY system
Cons
- None that we can see
9. Fluval Ceramic CO2 Diffuser
If you are using the Fluval brand pressurized CO2 system in a small aquarium with a capacity of less than 30 gallons, the ideal replacement is this small Fluval Ceramic CO2 Diffuser. With its large ceramic disc, this diffuser produces a constant stream of fine bubbles.
It’s easy to install, and while it’s not the prettiest device, it gets the job done. It is also a very cheap replacement part, which is handy. It is perfect for Fluval systems and will work with most pressurized CO2 generators as long as they produce at least 30 psi (pounds per square inch).
This is a very basic diffuser and comes with some protection for the ceramic disc and a suction cup to hold it in place.
However, the diffuser is not very easy to clean and the ceramic disc cannot be removed from the housing. While you can soak everything in bleach or hydrogen peroxide to remove any stains or algae, the fittings seem to wear out quickly and this diffuser needs to be replaced regularly.
The Fluval is harder to break than glass diffusers, so for some users it may be a more durable and cost-effective option. Even if you have to replace it more often because of its marginal quality, it probably won’t break if you remove it for maintenance.
Benefit
- Cheaper option
- Durable
- Easy to install
Cons
- No aesthetic appeal
- Not easy to clean
- Needs to be replaced regularly
10. Sera Flore CO2 Active Reactor 500
If you want the best CO2 reactor, the Sera Flore CO2 active reactor 500 is considered the top model for smaller aquariums. It is the ideal size for a planted tank under 160 gallons and works with pressurized and low pressure CO2 injectors. With two impeller blades, the Sera can spread up to 500 CO2 bubbles per minute in your aquarium.
The Sera can be installed in-line as part of your container filtration system, or you can use it with a pump in your aquarium. This flexibility allows you to position it in the optimal location based on your tank flow patterns and the location of your inlet and outlet lines.
CO2 reactors are significantly more efficient than other designs, so if you want to ensure that most of the CO2 in your system is available to your aquatic plants, this is the way to go.
Like all CO2 reactors, the Sera makes a lot of noise immediately after installation or maintenance, because air bubbles need time to escape. This isn’t the easiest diffuser to install either, but Sera has top-notch customer service and they are very helpful if you have any problems.
Benefit
- Location adaptability
- Efficient bubble production
Cons
- Difficult installation
- Noise during installation and maintanence
What is a CO2 Diffuser and What is its Purpose?
Aquarium plants absorb carbon dioxide and give oxygen to the water. That said, they need more carbon dioxide to thrive then what is available in most freshwater aquariums. That’s where a CO2 diffuser comes in.
Since CO2 is a gas, it takes some effort to dissolve it in water. Just bubbling won’t provide the levels that plant life need to thrive. Diffusers work in part by increasing the surface area of water exposed to the gas.
This is generally achieved by passing CO2 through a ceramic disc. This agitates the water and keeps it in contact with the CO2 for longer, allowing it to be absorbed more efficiently.
How to Choose the Best CO2 Diffuser ?
Start with your tank size
Size matters when it comes to CO2 diffusers. A diffuser designed for 10 gallons is not big enough for 55.
The surface of the ceramic disc needs to be large enough to suck up the amount of gas you need for that much water and a smaller diffuser is not designed to handle the higher pressure required for a larger tank.
On the other hand, when using a diffuser designed for a larger tank, lower CO2 pressures may not be able to push the gas through the ceramic disc.
That is why it is important to buy a diffuser that is appropriate for the size of your tank.
Think about the overall quality
With a lot of aquarium equipment, you get what you pay for. CO2 diffusers are no different. Yes, it seems that some diffusers cost a lot more than others when you’re shopping.
A cheaper diffuser could be less efficient and may need to be replaced more regularly. CO2 is not free, so having a diffuser that doesn’t distribute it well through the water is a waste of money.
Sometimes you need to consider usage costs over time rather than just price.
What does the kit include?
Some diffusers come with additional equipment such as U-turns, bubble counters and/or check valves.
If you base much of your choice on price, it’s important to consider whether you need to purchase additional equipment.
Best Place to Put a CO2 Diffuser in Aquarium
There are a few things to keep in mind when it comes to fitting a CO2 diffuser for optimal results.
First, it should settle near the bottom of the tank. The longer the bubbles stay in contact with the water, the more it will be absorbed. However, avoid placing it under the ground where the bubbles can be disrupted or blocked.
Avoid placing it between plants. While it may seem like this would be a good place to do it, as it benefits plants in the first place, it can cause unnecessary problems. You could run into the same problem as with the substrate, where bubbles to collect on the plants and mix into larger bubbles that are absorbed less effectively.
Remember that the goal is to circulate the CO2 bubbles as much as possible so they have more time to be absorbed. A good place to place it is under the filter return. That way, the water returning to the tank will push the bubbles down and they can circulate longer.
If you can’t place your diffuser that close to your filter, try placing it in a location where air bubbles are trapped in the flow created by the filter return.
Another thing to remember is that you may need to move the diffuser as plant life begins to grow. Don’t be afraid to adjust to your tank environment as you need to.
How to Install a CO2 Diffuser?
There are many different CO2 diffusers on the market and the installation of the varied models may be unique to each one. But here are some general guidelines:
Follow along the line from the CO2 tank to the aquarium.
The first device after your CO2 tank should be your check valve. This prevents water from flowing back into your CO2 tank when the pressure drops, for example when the power is turned off at night.
The next device should be your bubble counter (if you are using a separate device). This lets you know how fast gas is being fed into the system and allows you to increase/decrease the pressure and amount of CO2 pushed into the aquarium.
Next comes your U-bend. This is important because CO2 hoses can harden over time and bend where it bends over the edge of the tank.
The diffuser is the end of the line. You want to place it as low towards the bottom of the tank as possible. It’s totally fine if it’s just above the gravel. You want the bubbles to spend as much time underwater as possible.
Final Comments
In order for freshwater plants to thrive, most aquariums need extra CO2. By choosing the Best Aquarium CO2 Diffuser, carbon dioxide can be added effectively and your plants will have everything they need to thrive.
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