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Carbon dioxide (CO2) is a limiting factor for successful plant growth in freshwater aquariums. Without adequate CO2, it doesn’t matter how much light or fertilizer you offer your plants; they simply won’t grow as well as they could.
That’s why one should do plenty of research in order to find the best CO2 reactor and diffuser choices available. Without a good method of dispersing CO2 to your plants, you won’t get the greenery you’re looking for!
CO2 Reactors, Diffusers, and Atomizers
There are several ways to get carbon dioxide into your tank for plants to use. Therefore, I will be reviewing the following CO2 dispersal agents, from 3 product categories:
Co2 Reactors:
Co2 Diffusers:
Co2 Atomizers:
Why Should I Be Using CO2 in my Planted Aquarium?
As I mentioned earlier, carbon dioxide is essential for aquarium plants. It’s used in photosynthesis and broken down using chlorophyll and light to form the sugars plants need to survive. It’s also used in the structural carbohydrates (cellulose) that plants use to build themselves up!
CO2 in a planted tank ensures your plants can grow fast enough to absorb the fertilizer and make use of the available light. Without it, not only is it impossible for them to grow but algae becomes a real nuisance.
Algae are much simpler organisms than plants. They can thrive with the tiny amounts of CO2 that are always present and will use up the fertilizer and light you’re providing for your plants to coat everything in a green fuzz or slime.
In short: if you want lush plant growth that can outcompete algae for nutrients, a CO2 generator plus a dispersal system to get it into the water column is mandatory. But not all CO2 dispersing systems are created equally…
The Best CO2 Reactors, Diffusers, and Atomizers
The three main types of carbon dioxide dispersal systems are reactors, diffusers, and atomizers. All three rely on taking bubbles of pure CO2 and mixing it into the water column.
However, they differ in how effectively they mix the CO2. Reactors are designed to mix 100% of the bubbles into solution. This means there should be no bubbles or mist flowing into the tank.
This allows you to be incredibly efficient in how you use CO2 but the downside is that many plants actually prefer misting. While wasteful, it can actually result in as much as 25% more oxygen production during photosynthesis. Reactors are also larger than atomizers and diffusers.
Atomizers and diffusers take up significantly less space and are often less expensive. They create either fine bubbles or a very fine mist of CO2 bubbles that are released directly into the water column. You’ll have to rely on proper placement to try and keep the bubbles submerged long enough for them to dissolve. But a portion of your CO2 will be lost at the surface. Atomizers also require stronger CO2 pressure to create fine bubbles, unlike diffusers and reactors.
Now that we have a decent understanding of the differences between them, let’s take a look at some of the best CO2 reactors & diffusers available!
Carbon Dioxide Reactors
Sera Flore Active CO2 Reactor
If you’re looking for 100% dissolution of CO2 the Sera Flore Active CO2 Reactor does an excellent job of ensuring little to no bubbles enter your tank. The reactor uses an impeller to increase turbulence as CO2 enters the system. Water turbulence helps CO2 dissolve even better within the reactor before it gets released.
Since it relies on directly mixing water and CO2 together, you need to pair this with both a source of CO2 and a pump. The Sea Flore 500 is designed for pumps that operate on aquariums greater than 55 gallons; 250+ gallons per hour (GPH). Any less and the impellers won’t spin fast enough to properly dissolve your CO2 bubbles.
However, it’s extremely user-friendly and can be set up and running in mere minutes! No tools are required; simply follow the included diagrams.
Pros
- 100% CO2 dissolution
- Usable for medium to large planted tanks
- No diffuser stone to replace
- Entirely silent operation
Cons
- Too powerful for small aquariums
- Pricier relative to Diffusers and Atomizers
Gulfstream Tropical AGU00529 Ista Max Mix Co2 Reactor
The Gulfstream Tropical’s design allows it to essentially hold CO2 bubbles continually until they are broken up and forced to dissolve into the water. This ensures next to no bubbles or mist is released into the tank.
Thanks to its durable CO2-resistant plastic construction, the slight acidity dissolved CO2 introduces into the water doesn’t affect its long-term operation. Something to note is that the unit is not entirely silent. The impeller makes a slight rattling noise during operation but it’s faint enough to only be an issue in the quietest of locations.
Some users have found that the construction doesn’t quite compare with the Sera Flore models and that Gulfstream’s quality control isn’t on par. Beware of occasional leaks from poorly constructed units.
However, it’s extremely user-friendly and can be set up and running in mere minutes! No tools are required; simply follow the included diagrams.
Pros
- Rated for aquariums with pumps that have 250 to 500 GPH of flow
- 100% CO2 dissolution
- No need to replace a diffuser stone or other components
- Very fast and easy to set up
Cons
- Poor quality control
- Not entirely silent
Carbon Dioxide Diffusers
fibst CO2 Diffuser
The Gulfstream Tropical’s design allows it to essentially hold CO2 bubbles continually until they are broken up and forced to dissolve into the water. This ensures next to no bubbles or mist is released into the tank.
Thanks to its durable CO2-resistant plastic construction, the slight acidity dissolved CO2 introduces into the water doesn’t affect its long-term operation. Something to note is that the unit is not entirely silent. The impeller makes a slight rattling noise during operation but it’s faint enough to only be an issue in the quietest of locations.
Some users have found that the construction doesn’t quite compare with the Sera Flore models and that Gulfstream’s quality control isn’t on par. Beware of occasional leaks from poorly constructed units.
Fibst also offers a 6-month warranty on the ceramic disk, which is an excellent offer considering low-end disks can clog within 3 months. And their 24-month warranty covers any other parts that may break, though to be sure, a CO2 diffuser has few parts to begin with.
Pros
- Solid 304 Stainless Steel Construction
- 6-Month Warranty on the ceramic diffuser disk
- Attractive design matches any aquascape aesthetic
Cons
- Ideal for medium-sized aquariums (20-40 gallons)
- Medium-sized bubbles need recirculation to avoid wasting CO2
- Difficult to hide
Aquario Neo Co2 Diffuser
Thanks to its 304 Stainless Steel construction, the first CO2 Diffuser has a natural curvy elegance that makes it an artful addition to the technology supporting your planted tank.
By hanging on the side of the tank similar to an airline, it can be hidden or flaunted, as you prefer. And compared to glass models, metal CO2 diffusers are harder to damage and often have a larger dispersal zone for bubbles to form.
Many CO2 diffusers come with few to no instructions. Which makes running them bothersome because without occasional cleaning they tend to clog with algae and stop working. But the fibst CO2 Diffuser also comes with clear instructions on maintenance, cleaning, and even optimal pressurization to ensure the proper flow of bubbles.
While not on the level of a CO2 Atomizer the bubbles produced by the Aquario Neo are very fine. This allows them to stay submerged longer (when released into a current), helping them to dissolve more fully into the water. Just be sure that you soak it for around 3 hours beforehand to ensure water fully penetrates the ceramic disk.
Pros
- Especially fine-sized bubbles
- Clear acrylic construction allows the Aquario Neo to be hidden easily
- Twin suction cups to hold it in place
- Comes in several sizes (5-40 gallon aquariums)
Cons
- Best for medium-sized aquariums (40 gallons and under)
- Ceramic disks clog over time
JARDLI Pollen Glass CO2 Diffuser
Glass CO2 Diffusers are the best balance between aesthetics and discreteness. Whether you prefer to show off or hide your diffuser, the JARDLI Pollen Glass CO2 Diffuser is perfect for the purpose.
Another aspect of the JARDLI that makes it unique is the bubble counter at the base. CO2 is great for plants but too much can poison fish and invertebrates. Paired with a CO2 drop checker, the JARDLI design is ideal for ensuring you can gauge how much of the otherwise invisible gas is entering to keep both plants and animals healthy.
Glass diffusers are unfortunately the most fragile of the three main types (glass, plastic, metal) and breaks do occur. The JARDLI is also on the smaller side, making it perfect for planted nano tanks 20 gallons or less in size. But for medium to large aquariums, you’ll need a diffuser that can handle more CO2.
Pros
- Glass construction is resistant to wear and easy to hide or show off
- Bubble output is ideal for planted nano tanks (20 gallons and under)
- Design includes a bubble counter to accurately gauge how much CO2 is being added
Cons
- Too small for aquariums beyond 20 gallons in volume
- Glass is fragile and can shatter accidentally
CO2 Atomizers
NilocG Aquatics | Intense Atomic Inline Co2 Atomizer
NilocG Aquatics offers some of the finest planted aquarium products on the market and the Intense Atomic Inline Co2 Atomizer is no different.
As an in-line atomizer, it’s perfect for hiding somewhere outside of the aquarium itself. It connects to the outflow of a filter and a pressurized CO2 source. There, the atomizer mixes the water and CO2 before allowing it to continue onto the tank.
This model is designed specifically to be paired with the outflow of canister filters with an outflow tubing of 5/8ths of an inch. – You can use this atomizer with an aquarium of any size so long as the tubing is compatible (or an adapter is used).
The bubbles it creates are extremely fine; less than 0.1 mm in diameter. These microbubbles don’t race to the surface instantly and will float about the tank, slowly dissolving further. However, if they are slow to mix into the water column, the fog effect isn’t always appreciated.
NilocG promises 100% CO2 diffusion but this is more dependent on how you set up the flow in the tank. Assuming you place the outflow properly to maximize the time bubbles remain submerged, you can achieve 100% CO2 diffusion!
Pros
- Up to 100% CO2 diffusion
- Quiet, discreet, and quick to set up
- Can be used with any aquarium size
Cons
- 100% diffusion depends on how flow moves within your tank
- CO2 can form a “fog” that’s not aesthetically pleasing
- Pricey relative to CO2 Diffusers
Aqualexs Aquarium Inline Co2 Atomizer
While it’s rated as an atomizer this model doesn’t create bubbles as fine as the NilocG Aquatics design. Instead, Aqualexs tends to make a mixture of both super-fine and microbubbles, which means a small portion of the diffused CO2 will outgas at the surface.
The advantage it offers is as much an aesthetic one as it is functional! As an inline diffuser you can avoid unsightly technology hanging around the sides or within your tank. The Aqualexs also comes in two sizes, helping you to avoid having to match and purchase additional adapters to connect it to various sized tubing.
While this model is very capable, it takes some tweaking to ensure that you get optimal flow. For example, overtightening any of the three O-rings can result in gas leaking from the system. It can also be fully disassembled, making maintenance a snap! The unit can be thoroughly cleaned and the diffuser stone replaced in minutes.
Pros
- Easy to hide and quiet operation
- Two sizes for better pairing with various water sources
- Easily disassembled and cleaned
Cons
- Bubbles aren’t fine enough for 100% diffusion
- Improper setup can hamper diffusion
Which is the Best CO2 Dispersal System?
If I had to choose a single winning CO2 dispersal system for the majority of tanks, my choice would be the NilocG Aquatics Intense Atomic Inline Co2 Atomizer. It offers the best of both worlds in terms of features and aesthetics.
You can also get 100% diffusion just like a CO2 reactor but it’s also easy to hide and silent running, just like a diffuser. Lastly, it can be paired to an aquarium of any size.
However, if I wanted something small and affordable for a smaller planted nano aquarium, the best diffuser is the fibst CO2 Diffuser. The curved stainless steel is an attractive fit for most aquascapes. But the 6-month warranty on the high-quality CO2 ceramic diffuser is very handy because these always need maintenance or replacement over time.
Just make sure you pair your new dispersal device with a quality CO2 regulator as well!
Conclusion
While the NilocG and fibst models are my favorites, any one of these CO2 reactors, diffusers, or atomizers is going to get the job done! Whether you prefer no bubbles or large ones, what really matters is getting CO2 into your planted tank. With a good CO2 source your plant’s growth is guaranteed to take off like never before!
