Aquarium plants absorb carbon dioxide and release oxygen into the water. That said, they need more carbon dioxide to thrive than what is readily available in most freshwater aquariums. That’s where a CO2 diffuser comes in.
Because CO2 is a gas, it takes a little work to dissolve it into the water. Simply bubbling it through won’t provide the levels that plant life needs to thrive. Diffusers work in part by increasing the surface area of water exposed to the gas.
This is usually accomplished by feeding CO2 through a ceramic disc. This both agitates the water and keeps it in contact with the CO2 for longer periods of time, allowing it to be more effectively absorbed.
The 10 Best CO2 Diffusers for Your Aquariums
There are plenty of CO2 diffusers to choose from. While they all accomplish the same thing, there are various ways to go about it. Most are made of glass, some of stainless steel. They come in different sizes and shapes, too.
If you’re looking for the best CO2 diffuser for your aquarium, we’ve put together a list of the best ones available.
This CO2 diffuser is a great choice if you’re looking for something that makes micro-fine bubbles. Microbubbles help the CO2 diffuse quickly which makes it quickly available to your plants.
This diffuser is made of strong glass that won’t break easily. It’s also washable and can be used over and over again without needing to replace it.
Part of the reason that this diffuser is so effective is because it’s so lightweight and airy, which is why it’s able to produce so many fine bubbles. It’s bowl-shaped and has a ceramic disc with a lot of surface area for increased effectiveness.
2. JARDLI Pollen Glass CO2 Diffuser
This Pollen Glass diffuser comes in two different sizes, 1 ½ inch for a 20 to 50-gallon aquarium and 2 inches for 50 to 75-gallon. They’re small, efficient, and provide a beautiful display of bubbles.
This bowl-shaped diffuser is made of glass so they don’t distract from the natural beauty of the tank. Installation is easy, just use the two suction cups to attach the diffuser into a corner.
The ceramic membrane creates efficient CO2 atomization because it has a large surface to volume ratio to easily dissolve CO2. The fine bubbles are easily absorbed by plant life so they get just the right amount needed to thrive.
One of the best things about this diffuser is it’s very well made. The high-quality ceramic membrane is really effective and the glass is crystal clear and unobtrusive. To make sure the glass stays intact, wet the glass before inserting the tubing.
This diffuser is compatible with 4/6 mm CO2 tubing and should be used with a CO2 tank with an injection rate of at least 2 to 5 bubbles per second. For best results, make sure to soak all surfaces in water for at least 30 minutes before installation.
3. JARDLI Pollen Glass CO2 Diffuser with Bubble Counter
JARDLI’s CO2 diffuser is a great choice if you’re looking for something that’s going to blend into your tank. It creates small bubbles that look great in your tank while also providing your plants with an easy way to absorb what they need to grow. The ceramic membrane has a large surface area which is why it’s able to create so many bubbles.
This is a small diffuser, only 0.8 inches, and it’s meant to be used in tanks that are under 20 gallons. It’s compatible with 4/6 mm CO2 tubing and made with high-quality materials, including the glass and the ceramic membrane.
To make sure everything works properly, wet the glass tubing before attempting to attach any tubing. This will act as a lubricant and the tubing will slide right on without risking any damage.
Also, make sure to soak the ceramic disc, tube, and other surfaces for at least 30 minutes before using them.
4. Yagote CO2 Glass Aquarium Diffuser
The Yagote diffuser has a ceramic diffuser with atomic pores that produces fine bubbles that rise slowly. The cylindrical shape and smooth lines slow down the water so this makes sure that CO2 is thoroughly diffused throughout the water because the fine, slow-moving bubbles get absorbed quickly and completely.
It’s made of high-quality glass that won’t easily break and blends in well with the rest of your aquarium plants and decor.
Installation is really simple, just use the included suction cup to secure it to the inside of the aquarium. If you don’t like the positioning, it’s really easy to adjust.
The diffuser itself is made of high-quality glass materials and can’t be damaged easily and can be used in tanks ranging from 15 to 50 gallons. Plus, because it’s clear, it easily blends into the rest of your aquarium.
5. fibst CO2 Diffuser for Aquarium
This diffuser is a little different than the others we reviewed because it’s made out of stainless steel instead of glass. Stainless steel doesn’t rust or corrode so it will last a long time in your aquarium.
Plus, it adds a simple, elegant piece of art to the environment. It produces fine, round bubbles as opposed to partial bubbles that other diffusers make.
Cleaning is easy, all you have to do is turn the stainless steel cup to remove the ceramic sheet cover. Installation is really easy, too, just hook the diffuser over the edge of the tank and use the stainless steel fixture 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 sheet and 24 months for other parts.
6. Rhinox Nano CO2 Diffuser
We love the design of this CO2 diffuser from Rhinox. It uses a microbubble ceramic diffuser plate with extra-fine pores so the CO2 rises slowly in the water and the cylindrical shape helps slow down the speed so your plants can make the most of it.
This is an ideal choice for small tanks. The unobtrusive glass design isn’t very noticeable and doesn’t take up a lot of space while the tiny bubbles add movement and a visual feature to the tank while also being a practical way to help your plants thrive.
Setup is quick and easy, too. Just use the included suction cup to attach it to the tank. It’s compatible with pressurized tanks up to 20 gallons and each diffuser is handmade by an artisan glassmaker.
7. JARDLI Music Glass CO2 Diffuser for Aquarium Plant
This CO2 diffuser from JARDLI is designed for large tanks 75 gallons and above. The cool, artistic look isn’t intrusive and won’t take away from the aesthetics of the tank but still adds a bit of movement and visual appeal.
The large two-inch diameter and ceramic membrane create a wide mist of tiny CO2 bubbles. This is really important because it’s much easier for smaller bubbles to diffuse into the water which makes the CO2 usable for your plants.
It comes with two suctions cups for easy installation and the diffuser itself is made of high-quality borosilicate glass that’s very strong and durable. The build is excellent and it’s a great addition to any large plant aquarium.
8. ST International Aquarium Glass Diffuser
The ST International diffuser is a good choice for small tanks. It creates a fine stream of bubbles to optimize CO2 diffusion to keep your plants green and thriving. The simple and small glass design fits easily into small tanks so you get the benefits without taking up too much valuable space.
The high-quality glass should last a while with proper care. Use the included suction cup to attach the diffuser to the wall of your tank, connect your pressurized CO2 system, and you’re ready to go.
For the price, this diffuser is really effective. It creates an ideal stream of bubbles that’s well-controlled, meaning that nothing escapes around the sides so you get a nice, effective stream.
9. STARSIDE Aquarium CO2 Diffuser
This STARSIDE CO2 diffuser is made from high-quality material and features a U-shaped design that works with any top. Because it’s made of resin and not glass, it’s more resistant to bending and extremely durable.
It uses a ceramic disk that produces a steady stream of small bubbles that easily diffuse in the water to benefit your plants. Installation is easy, too, just use the suction cup to attach it to the side of the take and adjust the U-bend as necessary.
One of the best things about this design is that it’s very unobtrusive. The U-shaped section fits easily over the side of most rimless tanks and some tanks that have a rim, too. If the U-shaped portion doesn’t fit, the rest of the diffuser will still work with simple tubing.
10. Yosoo U-Shape DIY CO2 Diffuser
The Yosoo U-shaped CO2 diffuser is easy to install and operate. Use the included suction cup to attach it to the side of your tank and hook it up to your CO2 source. The small transparent design is easy to hide so it doesn’t distract from your tank decor.
We really like this one because it’s multifunctional. Not only is it an atomizer but it also acts as a check valve, bubble counter, and a U-shape air intake. The U-shaped joint makes it really easy to set up the tubing and the bubble counter is accurate and performs well.
The check valve is always handy to have and the aerator effectively produces the right size bubbles for diffusion. This is a simple design that’s highly effective and ideal for small to mid-sized aquariums.
Best Place to Put a CO2 Diffuser in Aquarium
There are a few things to think about when it comes to placing a CO2 diffuser to get optimal results.
First, it should sit close to the bottom of the tank. The more time the bubbles spend in contact with the water, the more it will be absorbed. You might be tempted to place it under the substrate, but this isn’t ideal. Why?
Because of the surface of the ceramic disc that releases the bubbles is blocked in any way, the bubbles won’t keep their small size. They collect and gather into the larger bubble, which doesn’t absorb as effectively.
You should also avoid placing it among plants. While it may seem that this would be a good place for it since it’s for the benefit of the plants in the first place, it can cause some problems. For one, you’ll run into the same problem as with the substrate, meaning the bubbles will collect on the plants and combine into larger bubbles.
Remember, the goal is to circulate the CO2 bubbles as much as possible, giving them as much time as you can to absorb. One good place to position it is under the filter return. That way, the water coming back into the tank will push the bubbles back down which is one way to keep them circulating longer.
If you’re unable to position your diffuser that close to your filter, try to put it in a place where the bubbles will get caught in the current created by the filter return. Again, this will keep the bubbles circulating and prevent them from surfacing too quickly.
One more thing to remember is that you might have to move the diffuser as the plant life begins to grow. When plants get taller and denser, the flow of the water will be affected and you can run into the same problems we mentioned earlier, bubbles collecting and becoming too large then quickly escaping to the surface.
How to Install a CO2 Diffuser?
Installation will be slightly different depending on the model you’re installing but here are the basics.
First, you’ll need a CO2 tank. It’s also highly recommended that you use a bubble counter. Fill the bubble counter tube ⅓ of the way with freshwater keeping the open end of the tubing submerged so it doesn’t suck in air. Make sure the O-ring is secure so there aren’t any leaks.
Mount the bubble counter to the side of the tank or wall so it’s easily visible. Then, cut tubing to connect the CO2 tank to the bubble counter. Leave a little bit of slack, you don’t want this fitting to be taut.
Next, connect the bubble counter to the CO2 diffuser with another length of tubing. Make sure you use enough tubing. Again, you don’t want it to be taut and you want to have enough length so you can make sure the positioning is correct. After they’re connected, place the diffuser into the tank.
Keep in mind that plants only absorb CO2 through photosynthesis so they’ll need sunlight or another light source. When it’s dark, they actually release CO2 so the diffuser shouldn’t be running if the light is turned off.
Conclusion
For freshwater plants to thrive, most aquariums need additional CO2. The only way to add it effectively is with a CO2 diffuser. By using the best one for your aquarium, your plants will have everything they need to thrive.
This JARDLI Pollen Glass CO2 Diffuser diffuser is awesome. I let this soak for a full 24 hours inside my tank before hooking it up to Co2. Thousands of tiny tiny bulbs flow from it while on. I’ve tried several other diffusers but this one produces the smallest bubbles in the largest volume from the ones I have personally used.
I have a 220 gallon planted aquarium. What would be the best co2 diffuse for this size tank?
This JARDLI Pollen Glass CO2 Diffuser diffuser is awesome. I let this soak for a full 24 hours inside my tank before hooking it up to Co2. Thousands of tiny tiny bulbs flow from it while on. I’ve tried several other diffusers but this one produces the smallest bubbles in the largest volume from the ones I have personally used.
Thanks so much for your helpful article.