Carbon dioxide (CO2) is one of the most critical nutrients for the plants in your aquarium. In its purest form, carbon dioxide is a gas. However, much like oxygen, it can be easily dissolved in water. Aquatic plants use dissolved CO2 to photosynthesize in a similar manner that regular garden variety plants would.
It’s worth noting that freshwater aquatic plants take in CO2 and expel oxygen throughout the tank water. They need more CO2 to flourish as to what is already derivable in your freshwater tank.
This is where an aquarium CO2 diffuser comes into play. A CO2 diffuser utilizes reactors or membranes to efficiently dissolve droplets of gaseous CO2 directly into the water inside of the aquarium, creating an ideal environment for your underwater plants to thrive.
There are many different aquarium CO2 diffusers available on the market. But which one is best for you? In this article, we’ll explore the top six best CO2 diffusers of 2020 reviews and offer you a comprehensive buying guide in order to find the right one for your aquatic landscape. Here are our top picks for the best aquarium CO2 diffusers of 2020.
A Quick Comparison (updated in 2023)
Image Product Details
Best Overall
Fluval
Easy to install
Affordable
Plastic body will not easily break
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Best Value
Rhinox Nano
High-quality material
Slows water down
Aesthetically pleasing
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Premium Choice
NilocG Aquatics Atomic Inline
Can be installed directly below or into the tank
Hard to break
Easy to clean
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JARDLI Pollen Glass
Built-in bubble counter
Can fit a number of tank sizes
Adjustable
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Aquario Neo CO2 Diffuser
Eye-pleasing clear acrylic
Works with a DIY system
Sturdy
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The 6 Best CO2 Diffusers for Aquariums
1. Fluval CO2 Ceramic Diffuser – Best Overall
It’s kind of an eyesore but luckily the small design makes it easy to hide it behind your fish tank plants. It also does not work well in big tanks and cannot be taken apart for cleaning purposes.
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All in all, we think this is the best CO2 diffuser for aquariums.
Plastic body will not easily break
Easy to install
Affordable
- Plastic body will not easily break
- Easy to install
- Affordable
Ugly
Doesn’t work in big tanks
Can’t be taken apart to clean
- Ugly
- Doesn’t work in big tanks
- Can’t be taken apart to clean
2. Rhinox Nano CO2 Diffuser – Best Value
The one drawback of this diffuser is that it works best in tanks 20 gallons and under. Some buyers have also complained that this diffuser is a tad noisy too.
Affordable
Aesthetically pleasing
High-quality material
Slows water down
- Affordable
- Aesthetically pleasing
- High-quality material
- Slows water down
Made for smaller tanks
Noisy
- Made for smaller tanks
- Noisy
3. NilocG Aquatics Atomic Inline CO2 Atomizer Diffuser – Premium Choice
It is on the pricey side of the spectrum. Additionally, when the solenoid cuts off, the product wills with water and sometimes fails. It’s also less pleasing to look at than other CO2 diffusers.
Easy to install
Easy to clean
Can be installed directly below or into the tank
Hard to break
- Easy to install
- Easy to clean
- Can be installed directly below or into the tank
- Hard to break
Expensive
Can fail if solenoid cuts off
Not visually appealing
- Expensive
- Can fail if solenoid cuts off
- Not visually appealing
4. JARDLI Pollen Glass CO2 Diffuser
Check Latest PriceThe JARDLI Pollen Glass CO2 Diffuser is a bell-shaped CO2 diffuser that has a built-in bubble counter. Water fills the bell in between the ceramic disk and tube. As the gas exits the tube, it will go through the diffuser’s fine points and creates a bubble. This eliminates the need for separate bubble counterparts. The height is adjustable, allowing it to easily fit in a large number of tank sizes.
It is made completely of glass, making it pretty to look at, but fragile. Additionally, you cannot remove the ceramic disk to clean it or replace it, and the kit doesn’t include a check valve or U-bend.
Built-in bubble counter
Adjustable
Can fit a number of tank sizes
- Built-in bubble counter
- Adjustable
- Can fit a number of tank sizes
Fragile
Cannot remove or replace the ceramic disk
No U-bend or check valve
- Fragile
- Cannot remove or replace the ceramic disk
- No U-bend or check valve
5. Aquario Neo CO2 Diffuser
The ceramic disk does not come off, so you cannot remove it to clean it or replace it. It also does not come with a check valve, U-bend, or bubble checker.
Eye-pleasing clear acrylic
Sturdy
Works with a DIY system
Available in small and medium sizes
- Eye-pleasing clear acrylic
- Sturdy
- Works with a DIY system
- Available in small and medium sizes
Ceramic disk does not come off
Does not come with a U-bend, bubble checker, or a check valve
- Ceramic disk does not come off
- Does not come with a U-bend, bubble checker, or a check valve
6. AQUATEK 3-in-1 CO2 Diffuser
Some users have reported that the CO2 was not being diffused properly by this product and bubbles were escaping from the inner silicone gasket circle and ceramic disk.
3-in-1 product
Made from sturdy ceramic
Won’t flood if power is lost
Affordable
- 3-in-1 product
- Made from sturdy ceramic
- Won’t flood if power is lost
- Affordable
CO2 can sometimes not be diffused correctly
Bubbles can escape
- CO2 can sometimes not be diffused correctly
- Bubbles can escape
Buyer’s Guide: Selecting the Best CO2 Diffuser For Your Aquarium
Devices and equipment for your aquarium can add up quickly. This is why it is wise to give your purchases some careful consideration before you buy. You want to ensure the aquarium CO2 diffuser matches your unique needs and style, and also optimally fits your tank size.
There are several things you should think about when choosing an aquarium CO2 diffuser, such as the materials it’s crafted from, the ease of use, the look of it, and its compatibility with your fish tank.
- Materials It’s Crafted from: The first thing to think about when you’re on the hunt for the perfect aquarium CO2 diffuser is the materials it is made from. Typically, most aquarium CO2 diffusers are made from glass or stainless steel materials. When made from glass, it is more pleasing to the eye as it has a mirror-like appearance when placed in the water. However, glass aquarium CO2 diffusers are a lot more fragile than stainless steel ones.
*However, stainless steel aquarium CO2 diffusers can look pretty ugly in your tank. But these types of models won’t break as easily as glass ones.
- Convenience and Ease of Usage: The second point of consideration when shopping for an aquarium CO2 diffuser is if it’s easy to install, take apart, and clean. Diffusers that come with ceramic discs are a lot easier to maintain because they only need a water/bleaching combination to clean them thoroughly.
*Some other models require the disc to be changed after a particular length of time. While it can be pricey, it doesn’t have the hassle of maintenance as a replacement ceramic disc doesn’t require any cleaning at all.
- How Compatible Is It with Your Fish Tank: It’s critical to inspect the aquarium CO2 diffuser’s compatibility with your fish tank’s size. Many aquarium CO2 diffusers are available in different sizes to cater to the tank size. You can figure out what size you need by the size of the diffuser’s ceramic disc.
*A general rule of thumb is that the smaller the ceramic disc is, the smaller the surface area for dispersing the CO2 bubbles needs to be. Thus, you will need to put it in a smaller tank size.
Aquarium CO2 diffusers that come with discs with a diameter size of two inches or bigger are recommended for large tank sizes, normally 70 gallons of water or bigger.
Aquarium CO2 Diffuser Frequently Asked Questions
How does an aquarium CO2 diffuser work? Your aquarium CO2 diffuser works by breaking down large bubbles into smaller ones to be dispensed throughout the aquarium. This will increase the carbon dioxide levels in the water of your fish tank.
How do I care for the diffuser? Aquarium CO2 diffusers are generally easy to care for, use, and operate. However, glass versions must be handled with care because they can break easily.
When it comes to cleaning the device, use a solution of water and bleach, and soak the product in clean water for 24 hours after. When storing your aquarium CO2 diffuser, keep it in a dry and cool area and away from children to prevent damaging it.
Are there different types of aquarium CO2 diffusers? Yes. There are a couple different types, including:
- CO2 Reactor: This is generally the most expensive type of aquarium CO2 diffuser and produces the largest output of CO2. It’s better for larger fish tanks.
- Ceramic Glass CO2 Diffuser: This kind of aquarium CO2 diffuser is fully submerged in the water and attaches to the tank glass with a sturdy suction cup. It’s a lot more affordable than a CO2 reactor and produces small and light bubbles.
- In-line CO2 Diffuser: This type of aquarium CO2 diffuser is helpful for larger fish tanks that contain a lot of gallons of water. It is highly effective and safe to use.
- Airstone Diffuser: We don’t recommend buying this type of diffuser. It makes large CO2 bubbles and this makes it tough for the carbon dioxide to spread evenly throughout the fish tank.
- Ladder CO2 Diffuser: This one is made for smaller-sized fish tanks. Its name comes from its ladder-like shape.
Benefits of Aquarium CO2 Diffusers
Your aquarium CO2 diffuser plays a vital role in the health of the aquatic plants growing inside of your aquarium. They use the CO2 bubbles the diffuser makes as their primary source of carbon.
Some of the perks of using an aquarium CO2 diffuser include:
- Healthy, thriving plants in your tank
- An affordable device that results in large, lush aquatic plants
- Works for mostly all kinds of plants
- Easy to use and operate
Conclusion
When all of the aquarium CO2 diffusers reviews are laid out on the line, the best one overall is the Fluval CO2 Ceramic Diffuser. It’s affordable, easy to install, and very durable. The best in value in our option is the Rhinox Nano CO2 Diffuser because it looks great in any tank, super affordable, and made from high-quality materials. It also slows the bubbles down so that your plants can get the most out of its use.
When you’re on the hunt for an aquarium CO2 diffuser, ensure that it properly fits your tank. You can do this by looking at the size of the ceramic disk.
For lush and gorgeous aquatic plants inside your fish tank, it’s important to utilize an aquarium CO2 diffuser to help them get the carbon they need to flourish.
