Finding the Best CO2 Regulator

As an Amazon Associate, we earn from qualifying purchases. The Witty Fish is reader-supported and we hope you love the products we recommend!

Carbon dioxide (CO2) regulators are an essential part of the planted aquarium keeper’s toolkit. But to safely bleed off CO2 in amounts small enough you need to ensure you have the best CO2 regulator you can get. Combined with a CO2 reactor, diffuser, or atomizer, the gas can then fully dissolve into your aquarium water.  

Introducing the Best Aquarium CO2 Regulators

There are several dozen CO2 reactors on the market today. But the following five models meet the requirements of the majority of aquarists.

I will be reviewing each of these in detail

Who Should Be Using a CO2 Regulator?

Aquarists with medium-sized to large aquariums (30+ gallons) will get the most out of a CO2 regulator. In smaller aquariums, you can often use DIY systems and smaller disposable CO2 canisters to meet the needs of your plants.

But for large volumes of water, you not only need a higher consistent output but enough CO2 to last you for weeks to months between refills. But the issue with canisters that large is that they have dangerously high pressurization levels to contain a high volume of carbon dioxide. 

In order to safely release it into our aquarium for dispersal and use by plants, we need to use a CO2 regulator! It uses an electric solenoid and needle valve that allows you to make ultra-fine adjustments to the flow. 

You can control the source, which is under immense pressure so that you can release as little as a few bubbles per second of CO2 into your tank. This slow drip of CO2 allows plants to slowly consume it. A CO2 regulator also ensures the dissolved gas levels remain low enough for fish to survive!

My Top Picks for the Best Aquarium Co2 Regulator

FZONE Aquarium Co2 Regulator

FZONE’s Aquarium Co2 Regulator is a high-quality unit that runs nearly silently while capably regulating even large pressurized canisters. An excellent feature included is the bubble counter that’s installed directly onto the unit. 

Typically, you’d have to purchase one separately and either add it in-line or use one built into your diffuser. Having the bubble counter directly on your regulator keeps everything involving pressurization in one location for instant measurements! 

The FZONE is also a low-power unit. Many CO2 regulators tend to run hot enough that they can be uncomfortably hot when touched. But this unit only consumes 2.5 Watts of power and stays cool despite continuous use. Being a DC solenoid instead of an AC unit, it’s also quieter running.

It does require an adapter if you’re using it for a paintball CO2 canister, meaning this design is meant for the largest CO2 canisters. The solenoid is also compatible with any electric timer and will shut down when the power is off. This means you can program an electric timer to power the solenoid on and off when your plants need CO2.

Lastly, you can make extremely fine adjustments with the control knob. While it can handle some of the largest plant CO2 tanks you can slow the flow down to as fine as 1 bubble per 3 seconds. 


  • Low Power Usage
  • Quiet, Cool Operation
  • Preinstalled Bubble Counter
  • Dual Pressure Gauge for accurate readings


  • Quiet buzzing sound audible in silent conditions
  • Paintball CO2 canister adapter not included

    S.T. International Aquarium 2-Gauge Professional CO2 Regulator

    As one of the best CO2 regulators you can get the S.T. International has twin pressure gauges to allow you to track both the internal tank and outgoing line pressurization. This is very handy if the outgoing pressure needs to be within a precise range for your CO2 reactor or atomizer!

    That said, S.T. International made the odd choice of using a rainbow background hue for the gauge. Combined with the golden metal construction it looks fancy. But the colors make reading the gauge for precision results more difficult versus a standard background. 

    I really would have liked to see a bubble counter installed on the unit, to visibly see how much CO2 is entering the system. Also, this model is extremely sensitive; slight adjustments can cause CO2 levels to move from too slow to too much. It takes a light touch to calibrate it for your aquarium. 

    That said, once you have it set, you don’t have to readjust it if you shut off and power it back on. Many low end CO2 regulators need to be calibrated daily once you power them back on, which can take many minutes to do.

    Lastly, there are no included instructions with this CO2 regulator. Assuming you’re already familiar with the setup and operation of one, it’s a very straightforward unit. But the lack of directions may be intimidating for a beginner.


    • Cool and quiet running
    • Twin pressure gauges that measure both internal and outgoing pressurization
    • Stable and needs no recalibration once you’ve found the right outgoing pressure


    • Multicolored Pressure Gauge difficult to read
    • No bubble counter mounted on unit
    • Very fine adjustments needed to change flow
    • No included instructions

      FZONE Aquarium CO2 Regulator Mini Series V3.0

      Smaller and medium sized aquariums can also reap the benefits of a CO2 regulator! The FZONE Mini V3.0 is compatible with smaller CO2 canisters, such as paintball canisters and disposable cartridges that use a 5/8ths inch thread. Keep in mind that a paintball-sized CO2 canister will still provide enough for a tank that’s 40 gallons in size.

      Many of the proprietary aquarium CO2 cartridges, such as Fluval’s, use a 3/8ths inch thread. But the good news is that disposable non-name brand cartridges are significantly cheaper than what Fluval offers anyway!

      The bubble counter included with this model is one of the best around. It serves its primary function of providing a visible gauge of how much CO2 is entering your tank. But it also acts as a check valve, preventing water from entering the line if the regulator powers down and depressurizes somehow. These are two devices you’d normally have to buy separately and install into your CO2 line so having them included and mounted onto your regulator is a real bonus!

      One thing I would have liked to see is twin pressure gauges that measure both internal and external pressure, rather than internal only. But considering the lower pressure of small tanks and the size of this unit, it makes sense to only have one gauge. The outgoing pressure can be adjusted from 0 to 45 psi – just know that the bubble counter is your only outflow gauge.


      • Combination bubble counter/check valve that’s mounted onto the regulator
      • Compatible with smaller CO2 canisters – ideal for small aquariums
      • All installation tools included, including Allen and crescent wrenches
      • Capable of extremely fine adjustments for slow bubble release


      • Designed specifically to regulate smaller canisters for small aquariums
      • Single gauge for only measuring the internal pressure

        Basic AQUATEK CO2 Regulator

        Aquatek makes sturdy, industrial-strength regulators and their Basic model is no exception. Instead of aluminum, Aquatek went with a sturdy brass construction that’s more durable as well as corrosion-resistant. Brass threading won’t strip easily despite continual use, which could otherwise lead to CO2 leaks. 

        The Basic CO2 Regulator also includes twin gauges that measure both internal and outgoing pressure. Unlike S.T. International’s fanciful styling, the basic is true to its name, with a simple, easily read color scheme. This unit is capable of being paired to tanks with a PSI of up to 3500 and regulating outflow as high as 140 PSI. This makes it excellent for larger tanks or as a master regulator for several smaller tanks.

        While it is cool to the touch and very durable, fine adjustments made to the flow may need re-adjustment over the course of a few days. Otherwise you may see the number of bubbles change over time. However it typically only takes seconds to minutes to ensure the flow is at your preferred level. 

        You do need a separate bubble counter and check valve installed. But Aquatek was nice enough to include a combination bubble counter/check value that you can install in-line instead!


        • Durable brass construction
        • Cool running solenoid
        • Designed for larger aquariums and CO2 canisters
        • Straightforward design for fast, accurate measurements
        • Includes a free bubble counter/check value in-line device


        • Occasionally needs fine-tuning of outflow over time
        • Bubble counter not integrated into the unit

          Premium AQUATEK CO2 Regulator

          Aquatek’s Basic model is fantastic but their Premium CO2 Regulator gives it a run for the money. The two units are very similar and the Premium design makes good use of the durable brass construction. Besides durability, another feature of brass is that it conducts heat more effectively than aluminum, helping it to remain cool to the touch. 

          Unlike Aquatek’s Basic CO2 Regulator, their premium design has a primary front control valve that allows you to control both the outgoing pressure and the flow. In essence, you have an additional measure of outflow control that lets you really fine-tune how CO2 enters your system. 

          The Premium Regulator can therefore be used on any size aquarium, potentially allowing you to step down the pressure within a huge canister to meet the needs of a small aquarium! It can be stepped down far enough to be paired with CO2 diffusers and atomizers of any size.

          It also includes twin regulator valves, allowing you to properly gauge both the internal and outgoing pressure values. And like the Basic model, Aquatek includes a free combination bubble counter and check valve that can be installed onto the outgoing line!


          • Extra front control valve for outgoing pressure regulation
          • Durable brass construction
          • Cool running solenoid
          • Designed for larger aquariums and CO2 canisters
          • Straightforward design for fast, accurate measurements
          • Includes a free bubble counter/check value in-line device


          • Occasionally needs fine-tuning of outflow over time
          • Bubble counter not integrated into the unit

            Which of these CO2 Regulators is the Overall Best Model?

            There is a lot to appreciate about each of these CO2 regulators. However, the one that will meet the needs of the majority of planted tank keepers has to be the Premium AQUATEK CO2 Regulator. 

            Besides its ability to gauge the pressure both incoming and outgoing, the further control the extra control regulator valve offers you ensures that you have ideal pressure for any kind of CO2 setup. Brass is also superior to aluminum for solenoid regulators in terms of durability and heat conduction. 

            While the Premium AQUATEK does need occasional fine-tuning it’s not as constant as the S.T. International. And a step-down adapter will let you attach it to smaller tanks just like the FZONE Mini!

            Why Should You Be Using a CO2 Regulator?

            A carbon dioxide regulator allows you to use large, pressurized CO2 canisters. If you have a medium or large planted tank and don’t want to mess around with tiny canisters, a large canister can provide weeks to months worth of CO2. Now that we have an idea of what models will meet our needs, what else is there to know about owning a CO2 regulator?

            Do I Even Need CO2?

            If you’re caring for aquarium plants that are anything other than the most basic in their care requirements (Java Moss, Java Fern, Hornwort, etc) then you should be supplementing with CO2. Plants require CO2 to build the sugars they need to survive and grow in size.

            The atmosphere has loads of it but it doesn’t dissolve into the water at levels high enough for sustained plant growth. In the wild, the decay of organic substances plus running water, which forces atmospheric gases into solution, provides a constant influx of CO2 for wild aquatic plants.

            In the home aquarium, there isn’t enough CO2 to truly thrive. Many kinds will grow slowly or not at all. But if you want to see your plants thrive, it takes supplemental CO2. Plus many ornamental species are dependent on high levels of CO2 for growth having been raised with rich CO2 levels for generations. 

            Things to Look For in a CO2 Regulator

            While most CO2 regulators are similar in their design and operation, there are a couple of factors to consider when shopping for one that are especially important.

            Needle Valve Fine Adjustment

            Having a needle valve capable of making ultrafine adjustments is very important in a quality CO2 regulator. When using low-quality models, the regulator may go from no flow to overwhelming in just a quick turn. Or it may take time for the flow to match the adjustments you’ve made, making it impossible to calibrate effectively.

            Twin Pressure Gauges

            Being able to monitor both the internal pressure and outgoing pressure is very handy if you are using a diffuser that requires a specific gas pressure for optimal operation. Many high-end diffusers and atomizers list this pressure range in their instruction manuals. 

            A single pressure gauge is still useful, and for CO2 regulators designed for smaller tanks, it may be all that you need. So long as you have some idea of the pressure inside of the system, you’ll be able to tell when the bottle or tank is running low and in need of a refill!

            Bubble Counters and Check Valves

            Once the CO2 leaves the regulator and starts traveling into the tubing, you may not have any easily visible sign of how much flow you’re getting. PSI ratings aren’t always helpful for knowing whether you have too much or too little CO2 entering the tank. A CO2 drop checker will tell you whether you’re in a safe or dangerous range for fish and other animals but it takes up to an hour to match your CO2 levels.

            This is where a bubble counter comes into play. For small and mid-sized tanks, knowing how many bubbles per second are being diffused into the water will ensure that you never reach levels poisonous to animals. Fish and other inhabitants typically start to show signs of stress above 30 ppm of CO2, or light green if using a liquid drop checker. 

            The exact number of bubbles per second depends entirely on your tank volume. But having an idea of this number will allow you to adjust the outflow so fish remain safe once you turn on and calibrate your CO2 regulator.

            A check valve is also essential for any tubing running from the aquarium to a low-lying external source. In case of a power outage, water can flow into and out of a tank in the same fashion as a gravity-powered siphon hose. A check valve is an inexpensive and simple way to prevent your tank from emptying in this way. 

            Many CO2 regulators provide a bubble counter and check valve for free that need to be installed in the outgoing CO2 line to the diffuser. And some models even build them into the regulator itself. I prefer this setup because it allows you to concentrate everything CO2-related in one place for fast reference!

            Tips to Remember When Using a CO2 Regulator

            CO2 tank with regulator and meter

            Use a Wrench to Tighten or Remove a Regulator

            The fit of the CO2 regulator needs to be air-tight, otherwise, it will leak CO2. While it’s possible to hand-tighten a regulator, ensuring it’s completely locked down with a crescent wrench is ideal. 

            Likewise, you’ll need a wrench to remove it without damaging the regulator or your hand. But make sure you don’t overtighten the regulator as it may cause damage to the device or strip the threads on the bottle.

            De-Pressurize the CO2 Regulator Before Removing It

            When removing the CO2 Regulator, don’t simply pop it off of the bottle. Depressurize it first by allowing any internal gas to outgas into the tank or air and then remove the regulator. This way, once you reattach it, you’ll have an accurate measure of the internal pressure of the CO2 canister.

            Using CO2 Tubing

            When buying a CO2 regulator, something that even pet store employees may not realize is that you can’t use silicone aquarium tubing. Standard airline tubing is semi-permeable to carbon dioxide molecules. Explained in another way, the CO2 molecules can actually push their way through the silicone material. When used in a pressurized CO2 system around 30% of the gas actually leaks right through the walls of the tubing! This will lead to tons of problems, obviously.

            You need to use CO2 tubing, which is usually (but not always) black in color to differentiate it from the clear, green, or blue standard airline tubing. When you have a ton of tubes running around your tank it pays to have that added layer of organization for fast referencing.

            CO2 tubing is pricier than standard airline tubing. But considering you won’t need more than a few feet of it it’s still very affordable and essential if you don’t want to be constantly leaking CO2 gas from your system.

            CO2 Reactors, Diffusers, and Atomizers

            The last step to running a CO2 Regulator is having a diffuser to break up the flow of CO2 gas so that it effectively mixes into your aquarium water. The three main ways to do so is to use a CO2 reactor, diffuser, or atomizer. 

            CO2 reactors are the largest but are also the most effective way to disperse CO2 into your aquarium water. If you’re looking for 100% dissolution, a reactor is the way to go. It uses a miniature impeller, similar to the one found in a power filter, to churn the CO2 gas into the water. The reactor then holds it there until the gas fully dissolves and then sends the enriched water into your tank!

            Diffuser and atomizers are simpler in operation. They create visible bubbles of CO2 that may slowly float to the surface (diffuser) or float about the tank for an extended period (atomizer). Which model you go with depends mostly on your aesthetic desires and your plant’s requirements. 

            All three systems are highly effective ways of getting CO2 into your water. And in case you’re interested in further reading, I cover this topic extensively in my article on CO2 Reactors and Diffusers!


            Choosing an aquarium CO2 regulator need not be a stressful event. While there are a ton of great choices in today’s market, there are a few that stand out from the rest. And now that you know how to operate your regulator and find accessories to manage its outflow, you’re well on your way to growing that lush aquascape you’ve always dreamed of!