There are many moving parts to consider when setting up an aquarium, and if you plan on having any types of plants inside yours, you’ll need to make sure they’re cared for as well.
Fish love being surrounded by plants in the water, and it creates a natural environment that they’re inherently used to, which is why most aquariums have them around.
However, for a plant to thrive and grow, it needs carbon dioxide, but this isn’t just a naturally occurring thing. Using a CO2 bubbler or CO2 diffuser is the most common method in a fish tank and the easiest approach but choosing the right fit for your tank can be overwhelming and confusing.
So, what is the best CO2 diffuser for an aquarium?
There are a few styles of diffuser to consider including ceramic, glass, plastic, air stones, and more, and the option for either submersible or external attachments.
To choose the right one for your tank, you’ll need to match the size and plant requirements, as well as determine how much maintenance and setup you’re happy with.
If you’re in the market for aquarium CO2 diffusers, you’ve come to the right place, as we’ve hand-picked a selection of the top rated ones. With our recommendations, you’ll find the best CO2 diffuser for your fish and plant life, and have the happy, thriving aquarium that they deserve.
A well-equipped aquarium that features both marine and plant life won’t survive long without carbon dioxide, so investing in a CO2 diffuser is a must-have. These are our picks for the best CO2 diffuser aquarium models so your aquatic plants can be as healthy and thriving as possible.
Our Expert Picks for the Best CO2 Aquarium
BEST CO2 DEFFUSER Jardli U-Shape Pollen Glass Diffuser
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Winner: Jardli U-Shape Pollen Glass Diffuser
- Type: Ceramic
- Diameter: 1.5 inches
- Fish tank size: 30 to 50 gallons
- PSI: 30
Jardli is a trusted name when it comes to aquarium accessories and if you want the best glass CO2 diffuser, their U-Shape model is our favorite.
This fish tank diffuser is 1.5 inches in size and comes with everything you need to set up with ease. Included in this package from Jardli, you’ll get the pollen CO2 diffuser, a glass U-shape tub, and two suction cups, and it can be put together in minutes.
The best thing about the Jardli U-Shape Glass Diffuser is the unique shape that prevents blockages from occurring.
Some other CO2 diffusers suffer from this issue and find that CO2 gets blocked on the way out, but Jardli have designed theirs with this specific issue in mind, and customers are thrilled.
Although it’s our favorite pick, the major drawback of this diffuser is its fragility. You’ll need to be very careful handling it and setting it up, as a few customers found theirs snapped or shattered with just minimal impact.
Take the care needed during this phase and it’ll reward you with years to come, but we would have preferred something more durable.
This 1.5-inch glass diffuser from Jardli suits tanks between 30 to 50 gallons in size and offers an efficient way to atomize CO2 using the ceramic membrane.
They also make a larger option with a 2-inch diameter for tanks up to 80 gallons if you have a bigger aquarium. The diffuser suits 4/6mm CO2 tubing for more setups and it’s easy to assemble everything in the tank.
The ceramic membrane of the Jardli U-Shape Glass Diffuser allows for up to 98% of CO2 running through it to be dissolved which is then spread through the tank in an easier format and it’s situated on a high-quality glass tube.
After just one day of running the diffuser, you should notice a drastic improvement in plant life, and thanks to the strong suction cups included, it’ll stay in place for years to come.
This powerful diffuser from Jardli is available online at Amazon for around $20 for the 1.5-inch size, giving you lots of power for the price. Amazon offers free returns and free shipping to your door when you spend over $35, but unfortunately, there’s no word of a warranty from Jardli.
The Jardli U-Shape Glass Diffuser is a must-have for any plant based aquariums and works quickly and efficiently to atomize the CO2 and make the ideal living conditions for everyone inside.
Runner Up: Jardli J-Shape Pollen Glass Diffuser
- Type: Glass
- Diameter: 0.8 inches
- Fish tank size: 20 gallons
- PSI: N/A
Another great fish tank diffuser from Jardli is their smaller glass pollen diffuser with a special J-shape design.
This model is only 0.8 inches in diameter so better suited to smaller tanks, with a maximum capacity of 20 gallons. Made with premium glass and sleek in design, it fits in well with all types of fish and plants without stealing the show.
This diffuser is very appealing aesthetically and it was a customer favorite because of its sleek design and how well it blended in with the rest of the tank.
Rather than having something bulky, plastic, or another color, the transparent glass can hardly be seen so it’s one of the better looking diffusers on the market. At less than an inch in diameter, it’ll hide away neatly, and not distract from whatever else you have growing inside.
On the downside though, people found the bubble counter not to be as effective as they’d hoped for which was disappointed for something from Jardli.
Some reported that after a month or so it started working so it’s not what you’d hope for in a new product, and others even had to blow on theirs just to get the water moving through it. If this occurs, you can return it for a replacement, or try to soak it longer during setup to see if it helps.
The Jardli J-Shape Pollen Glass Diffuser has an easy set up and includes a guide with detailed instructions.
To set it up, you’ll need to leave most parts soak for around half an hour, and handle the glass carefully as it’s fragile. Jardli recommends using silicone tubing as it’s a fragile and small diffuser that needs to be attached with care.
Jardli recommends using a specialized glass cleaner for this diffuser, and you’ll have to stay on top of it to prevent algae build up.
The diffuser comes with two heavy-duty suction cups that keep it connected to the tank wall, and it performs surprisingly well underwater so you never have to second guess its staying power.
Alongside the glass diffuser is a ceramic membrane that helps dissolve bubbles and provides an even distribution of CO2 through the tank.
To equip your home aquarium with this unique J-shaped glass diffuser from Jardli, go to Amazon to find the lowest online price. They have this listed for around $18 plus a small shipping fee unless you invest in two and qualify for free postage.
Although there’s no warranty offered by the brand because of its fragile nature, Amazon provides free returns should there be any issues. Jardli is a trusted name in aquatics supplies and this attractive glass diffuser proves exactly why.
Alternative: Fzone Aquarium CO2 Generator System Kit
- Type: Kit
- Diameter: N/A
- Fish tank size: N/A
- PSI: 1137
Fzone has created a complete CO2 Generator System Kit that goes above and beyond what a standard CO2 diffuser does, for those who want a DIY approach.
This kit includes a 2.5L stainless bottle, precision needle valve, regulator, and bubble counter, giving you a comprehensive way to deliver the CO2 that your aquarium plants so sorely need.
The best thing about this kit from Fzone is that it allows for a fully hands-off experience and provides everything you need to get it.
You’ll be able to purchase an additional solenoid that can be set up on a timer that injects CO2 into the tank as needed. Customers loved the option for automation that this offered and made it a lot easier to take care of their fish.
On the downside, there’s a fair bit to set up when it arrives, and although a cheaper option, some say you can tell where the corners have been cut.
This kit isn’t designed to last for years to come but is a good entry-level CO2 generator system and saves you from buying other expensive alternatives, but putting it together requires intermediate knowledge.
The Fzone Aquarium CO2 Generator System is safe to use and the bottle is made of 1.5mm thick stainless steel that’s able to sustain pressure up to 1137 PSI. If the pressure exceeds this point, the included safety valve will release, so you can feel safe about using it even if you’ve never had a DIY CO2 system before.
Other notable qualities of the Fzone System are the needle valve that achieves a steady rate of 1 bps and is continuously accurate.
The bubble counter has a built in valve as well, and its job is to prevent water from flowing back into the tank, so there are lots of features in place that will keep this CO2 generator doing its job.
If you want a DIY CO2 generator kit that doesn’t cost a fortune, the Fzone Aquarium CO2 Generator System is a great pick, although there’s no warranty coverage specified by the brand.
However, this is an affordable way to create your tank setup and ensure CO2 is delivered to your aquatic plants, costing just under $90 when you purchase online at Amazon and being shipped to your door for free.
Alternative: Niloc G Aquatics Co2 Atomizer Diffuser
- Type: Plastic
- Diameter: 0.5 inches
- Fish tank size: N/A
- PSI: 40
For fish lovers who have larger needs in their aquarium, you might prefer something more powerful like the Niloc G AquaticsInline CO2 Diffuser.
This diffuser is made with a durable plastic body and a ceramic plate that efficiently atomizes CO2 and spreads it throughout the tank. With a ½ inch diameter, it’s a lot more powerful than it seems, and needs between 35 to 40 PSI to work correctly.
According to customers, their favorite thing about this diffuser is how easy it was to install, especially for aquarium beginners. You can mount it underneath or straight onto the aquarium and it doesn’t have any small and fiddly parts, so long as you are careful with the ceramic plate that does the diffusing work.
However, it’s not the most visually appealing diffuser, and if you take a lot of pride in how your aquarium looks, you might find it downright ugly.
With a plastic construction and gray coloring that stands out in the transparent water, it could do with an upgrade. The Niloc G Diffuser gets the job done and is good value for money, but there’s nothing discreet about it and it can bring down the entire look of a tank that you’ve gone to a lot of trouble making nice.
Looks aside, there are plenty of other features worth discussing in the Niloc G Aquatics Inline CO2 Diffuser, and it’s got a lot on offer something in this price range and capacity.
This inline diffuser fits into ½ tubing and should only be used with CO2 specific tubing made of silicone preferably. The inner diameter is ½ inch and there’s another option available from the brand for a 5/8 inch that costs the same if you don’t require as much power.
Once installed, your Niloc G Aquatics Inline CO2 Diffuser will take the larger bubbles and create them into a fine mist that’s spread through the tank.
The superfine CO2 will be 100% dissolved in water which means healthier plants and a thriving aquarium without any extra effort required. The average size of each bubble is measured at less than 0.1mm in diameter, making it a force to be reckoned with compared to other diffusers we’ve seen.
To get your hands on the Niloc G Aquatics Inline CO2 Diffuser, head to Amazon to grab it for around $40 for the ½ inch size.
Amazon will ship your new diffuser for free and offer you free returns should you need it, but there’s no word from Niloc G Aquatics on a warranty. If you have larger needs and don’t mind accessories that aren’t as pretty, this is the diffuser to go with.
Alternative: ST International Aquarium Glass Diffuser
- Type: Glass
- Diameter: 0.8 inches
- Fish tank size: N/A
- PSI: N/A
If you’re shopping on a budget but still want the aesthetics of a glass diffuser to equip your fish tank with, the ST International Aquarium Glass Diffuser will be right up your alley.
This glass diffuser measures 2.8 x 0.8 x 1.8 inches making it a compact option, and it allows you to deliver a healthy dose of CO2 to the plant life within your aquarium. This simple diffuser comes with just one suction cup to keep it in place inside of the tank and will last for years with the proper care.
The best thing about this diffuser from ST International is how it looks. If you’re someone who opts for the minimal approach in your fish tank, it’ll fit right in and it’s sleek, small and see-through.
Fish owners who prefer the main focus to be on their livestock will love the simplicity of it and you won’t be able to see a thing other than the minimal mist it creates and delivers to the rest of the tank.
Compared to others we’ve reviewed, the fineness of the bubbles coming through this isn’t anything as impressive.
Unless you’re working on a budget or only have minimal CO2 needs for your aquarium plants, you’ll want to pay for an upgrade. Customers assumed it would be more adequate at distributing CO2, but it appears this is just an entry-level model.
The ST International still has a lot to offer for those with smaller tanks and minimal needs, including the fine craftsmanship of the glass itself.
Although fragile, the overall look is sleek, and it has high-quality glass that must be handled with care during installation. The process is easy and there’s one suction cup that is used to fasten it to the inside of the tank once it’s been attached to the CO2 pump.
The diameter of the ST International Aquarium Glass Diffuser is 0.8 inches and it’s suitable for around 20-gallon tank sizes, although people have found better results with smaller aquariums.
It works best with silicone tubing and can be attached to most standard CO2 systems designed for fish tanks, so as long as you have the right capacity it should work a treat.
Although small and better suited to basic setups, the Aquarium Glass Diffuser by ST International is a budget friendly pick.
You can get this diffuser for around $6 on Amazon, making it our cheapest find by far, and still deliver the CO2 that your tank’s plants need.
Keep in mind, Amazon charges a small fee for shipping, but there are loads of other aquarium products to suit the diffuser that can be bundled to save, so you have further chances to cut costs.
FAQs of CO2 Diffusers for Aquariums
A CO2 diffuser is not a necessity for all tanks but if you plan on having genuine plant life in yours, they’re a must-have. These attachments can be complicated to get a handle on, so we’ve answered some commonly asked questions that beginners have to help you understand them further.
What Does Co2 Do For Fish Tank?
The main nutrient for plants in an aquarium is CO2 as it helps them to grow and thrive.
As there is no naturally occurring CO2 in the water, and only a small amount is released from the fish and bacteria inside the aquarium, buying a diffuser or bubble is essential for aquatic plants.
How Much Co2 Does My Aquarium Need?
There is a fine balance of CO2 required in a fish tank, as having too much or too little can be bad for all concerned.
A general rule is that CO2 of 30 parts per million (ppm) is adequate but it will depend on the fish and inverts living in the aquarium.
Where Should Co2 Diffuser Be Placed In The Aquarium?
The placement of a CO2 diffuser is crucial in its effectiveness, so aim to keep it in the downwash current or as advised by the manufacturer when reading the setup instructions.
This enables the bubbles to be carried through the tank and to the other end, which provides an adequate supply through the entire area and ensures you’re using it as intended.
What Is The Use Of A Co2 Diffuser In An Aquarium?
A diffuser is used alongside a CO2 bubbler and it can help break down these air bubbles into smaller ones, which make them dissolve in the tank easier.
This ensures the carbon dioxide is spread throughout the tank and in an easier method than using just the big bubbles that come from a bubbler.
The Key to Thriving Aquatic Life
Owning an aquarium takes a lot of responsibility, and not just taking care of the fish that you have to worry about. The aquatic plant life inside of a tank is just as important as they provide a lot of good for the fish as well, so anything you can do to keep them healthy and thriving is essential.
A CO2 is a requirement for tanks with plants, and any of our top picks for CO2 diffusers will serve your aquarium well, so all you have to do is shop for the best fit for your tank.
This one addition will boost the health of your tank and all of its occupants, making it a must-have accessory for anyone serious about owning a plant filled aquarium.
I’ve been keeping fish for over 30 years and currently have 4 different aquariums – it’s an addiction. I’m here to teach you everything there is to know about fishkeeping.
I also use this site as an excuse to spend lots of money on testing and reviewing different aquarium products! You can find my reviews here.