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There’s nothing quite as lovely as a healthy planted aquarium filled with happy fish and vibrant plants. A CO2 system for your aquarium can definitely help with that.

And while you can have such an aquarium with very little equipment and limited work involved, there are definitely some devices and accessories you can add.

A special collection of these devices will increase the value of life your plants, fish, and other critters have, without much extra work for yourself. One of those devices is a CO2 for aquarium plants system.

Below, we’ll outline exactly how to choose the best aquarium CO2 system for planted tanks.

Best Aquarium CO2 System Quick-Find Table

Image Product

  • Great safety features
  • Professional DIY kit
  • Needle valve with bubble counter
  • Great safety features
  • Professional DIY kit
  • Needle valve with bubble counter

  • Great safety features
  • Complete setup kit
  • Runs on very low voltage and produces almost no heat
  • Great safety features
  • Complete setup kit
  • Runs on very low voltage and produces almost no heat

  • Professional quality
  • High capacity
  • Refined bubble control
  • Professional quality
  • High capacity
  • Refined bubble control

What is a CO2 System and Why Would You Want One for Your Aquarium?


Live plants need two things to grow healthy and strong: light and CO2 (carbon dioxide).

CO2 is required for respiration by aquatic plants, and they use this along with the light to go through the process of photosynthesis.

They need a constant supply of this CO2 much like we need constant supplies of oxygen. They combine the water, CO2, and light to produce that oxygen we need and the sugars they need for growth.

In the wild, plants get CO2 from natural substrate like mud and decaying plant matter. But in an enclosed environment like an aquarium, they don’t have as much access to CO2 for their growth processes.

We work hard to remove substances from aquariums that might provide plants with these materials, so sometimes they really struggle to get enough CO2 to grow well.

Author note: So, simply put, a CO2 system is an injector system that adds CO2 to your aquarium environment for the enhancement of plant growth.

What Kind of Aquariums Need a CO2 System?

Whether or not you need a CO2 injector or not depends heavily on the type of aquarium you keep, how much light your aquarium receives?

And whether or not you use fertilizers and other materials to supply your aquarium with the proper nutrient sources.

Top tip: The primary type of aquarium that would benefit from a CO2 injector or an automatic CO2 system aquarium setup would be a planted aquarium.

Reef tanks, marine tanks, and fish-only tanks rarely – if ever – need additional CO2 beyond what naturally occurs there.

And technically, planted aquariums do not require an aquarium CO2 system. If you want thriving, gloriously growing plants, however, you will find this easiest with such a system.

Author note: Low light aquariums are less likely to need a CO2 injector for plant growth stimulation.

The break down of dead plant matter, fish respiration, and surface agitation are usually enough to provide the necessary CO2. However, the low light aquarium could still benefit from an aquarium CO2 system, it’s just not quite as vital.

When we start talking medium and high light aquariums, however, CO2 injection becomes nearly vital.

The more light that’s available to plants, the quicker they grow. The quicker they grow, the more they need CO2. To meet that need for the high demand of CO2, a fish tank CO2 tank system and aquarium chiller is practically mandatory.

Without it, your fish tank is likely to produce algae and have other similar issues.

Benefits of Using a CO2 System in Your Aquarium


There are a few specific things plants in any environment need to grow: CO2, soil – or at least the nutrients received through soil – and light.

For aquariums without plants, CO2 systems aren’t particularly beneficial, but planted aquariums need the CO2 in most cases.

While our aquariums are not a natural setting for plants, we can do a few things to come closer to simulating that natural environment for them.

One of those is providing them with higher CO2 or carbon dioxide to increase and improve growth rates.

Low carbon dioxide levels aren’t very natural for your plants, so using the best aquarium CO2 system will give the planted aquarium an instant redirect towards a more natural environment.

In their natural environment, plants ingest CO2 through the substrate provided by mud, decaying plants, et cetera.

But since your aquarium is a small, closed ecosystem, you don’t have the luxury of leaving those elements in your substrate. In fact, if you do, your fish can become ill.

Author note: In your aquarium, the CO2 is naturally lower because the substrate imitates a natural landscape, rather than providing actual decaying plants, et cetera, and this throws off the balance. This imbalance affects the health of your plants.

Required Tools and Pieces for a Complete CO2 System for Aquarium Setup

Newly populated fresh aquarium with planted algae, no fish

There are several parts to your CO2 generator aquarium setup.

Most – or all – will come with your system when you purchase it, but for a better understanding of what you’re doing and what you’re getting into.

Here’s a short breakdown on the info on what’s involved and what to look out for in your aquarium CO2 system.

The CO2 SYstem Bottle

CO2 – or carbon dioxide – comes in several bottle sizes, similar to propane tanks you’d purchase for your grill or camping stove. And, not to be too obvious, but the larger the bottle, the more CO2 you get.

Top tip: To save money on your CO2, you can look for wholesale sellers for long-term savings.


The solenoid acts as the system automation tool. This disables the injection of CO2 into the aquarium, based on an attached timer.

The solenoid makes your CO2 system for aquariums more self-sufficient and therefore easier to use and maintain over time.

If, for example, you’re away from home for a longer time than usual, the solenoid tells the system to turn off automatically. Less CO2, less stress for you.


The regulator is the portion of the system that acts as the injection tool. The regulator releases pressure from the bottle to lower and manage the output pressure.

Typically, a regulator comes with a gauge that allows you to monitor the rate of injection so that you can adjust and make the proper changes necessary for the right amount of CO2 into your aquarium.


The diffuser is the part of the system that inserts the CO2 into the aquarium. The diffuser is made from a porous material that injects the CO2 into the tank via a fine mist of bubbles.

It also functions to disperse the CO2 gas throughout the entire aquarium water so that it’s most effectively used by the entire plant colony in your fish tank.

Bubble Counter

The metric tool used to quantify the CO2 levels pushed into your aquarium is called the bubble counter. This part of the equipment is usually added to your filter.

It measures the rate of bubbles exported per second and helps you determine if your aquarium needs less or more carbon dioxide.

CO2 Drop Checker

A color-coded gauge measuring the concentration of CO2 in your aquarium water is the drop checker.

Unlike the regulator and bubble counter, the drop checker measures the rate of injection, giving you a clear understanding of CO2 saturation in your aquarium ecosystem.

This provides a better understanding of the health of your aquarium.

Author note: Too much CO2 is unhealthy for your fish, but too little won’t help your plants grow.

CO2 Tubing

The final component of your aquarium CO2 system is the tubing. This tubing works as the connector between your regulator and diffuser.

It’s important to choose the right tubing, though, as not all tubing is created equal. Look for tubing that’s CO2 tolerant.

CO2 System Types

Fresh water planted aquarium with silver angelfish

There are three basic types of CO2 systems that may or may not be suitable for your circumstances.

Manual CO2 System

Most manual CO2 systems basically function as yeast fermentation systems. CO2 is generates as a metabolic byproduct of yeast and is stored in the fermentation canister.

The accumulated CO2 travels through a reaction chamber and then mixes with the aquarium water via the powerhead or diffuser.

Manual CO2 systems are suitable for smaller planted aquariums.

Semi-Automatic CO2 System

Semi-automatic CO2 systems require a bit more effort initially for installation but work from a timer-operated system to help simplify the process of injection.

The semi-auto system uses the solenoid, bubble counter, diffuser, and regulator to work through timer operated setup for a set period of time – such as when the lights in your aquarium are on – to supply the plants with carbon dioxide.

These systems are best suited for medium-sized and larger planted aquariums.

Automatic CO2 Systems

Similar to semi-auto systems, the fully automatic CO2 system uses the same components, but add in a pH controller and probe.

The upgrade in technology constantly monitors the aquariums pH levels while the prove detects pH level drops below the set point.

If the difference is within specific parameters, the system automatically shuts off the CO2 flow to prevent further changes.

These systems work for aquariums of all sizes but especially benefit heavily planted or large aquariums.

Reviews of the Best Aquarium CO2 System Options

CO2 system fish tank

To find the best aquarium co2 system options available, we dug around the various online reviews from professionals and hobbyists alike before diving into our own research.

We culled through the list by knocking out obviously paid reviews and then used these elements to determine the best options available.

Then we did our own in-depth reviews and research on each aquarium CO2 system to determine the best choices for your aquarium setups. We looked at the following parameters when deciding on our top picks:

  • Trusted brand names – with a reputation for quality, durability, and customer service
  • Ease of use and maintenance – can pretty much anyone use it?
  • Value for the price – quality appropriate to the price range
  • Various tank and plant needs – multiple options for various setups
  • Type of material – glass, metal, acrylic
  • Low profile – to avoid messing with that important aesthetic



The FZone CO2 kit is a professional DIY setup, meaning it’s got the top notch quality you’re looking for, but in an affordable DIY packaging option.

The kit includes a 2.5 liter stainless steel bottle, regulator, precision needle valve, and an easily adjustable bubble counter.

The bubble counter is a high precision counter that provides you with highly accurate fine-tuning for your CO2 injection needs.

Here’s the breakdown:

  • Cost effective: Most budget-friendly on our list
  • Comes with: steel bottle, regulator, precision needle valve, adjustable bubble counter, optional solenoid

What We Loved

The first and foremost on this CO2 injection system from FZone is that it’s truly a high quality device that will get the job done – and get it done well.

The equipment components that come with the system are top notch but easy to use and understand the fine-tuning tweaks you can make with it.

We love the safety valve that automatically opens when the inside pressure becomes too high – saving your fish, the aquarium, and the CO2 system.

The steady precision of the bubble counter is another top-notch part of this. You can get the steady 1 bps going with this.

Plus the bubble counter stops the back flowing water problem not always accounted for in other systems.

Plus, this system is great for many tank types, including nano reef tanks.

What We Didn’t Love

If you opt for the add-on solenoid, the aluminum couplings aren’t always as strong as they ought to be.

Otherwise, there’s really nothing to complain about on this one.

Our Verdict on the FZone CO2 System

The FZone CO2 system is a pretty great option all around. The kit is designed as a professional grade piece of equipment with easy to use controls so anyone can use it.

The CO2 system is smooth running, regular, works as promised, and generally is just a darn good investment for your aquarium setup.

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Magtool COs system

The MagTool CO2 system is another great choice in professional grade CO2 systems for your aquarium.

The MagTool comes complete with a 4 liter stainless steel bottle, DC mini solenoid, regulator, precision needle valve, bubble counter, and CO2 diffuser.

It also comes with a CO2 graded tubing, a plastic funnel, and measuring cup for a complete setup.

The MagTool has high safety standards with a built-in safety valve that opens automatically when the inside pressure is too great, preventing damage and danger.

The solenoid runs on very low voltage as well, and generates almost no heat.

Here’s the breakdown:

  • Cost effective: A little pricier than the other models on the list
  • Comes with: 4 liter bottle, DC mini solenoid, regulator, precision needle valve, bubble counter, CO2 diffuser, CO2 graded tubing, plastic funnel, measuring cup

What We Loved

The MagTool is an amazingly efficient CO2 system for the aquarium. It runs well, it does the work it promises, and it doesn’t create a lot of hassles.

We love that the kit comes with everything you need to set it up, including a mini solenoid.

We also love the safety features and quality of the manufacture that helps to make sure your aquarium and all the equipment remains safe to use.

The solenoid/bubble counter combo has a quick plug connection, with a one second plug in and take off.

The system uses low power and is cool to the touch, making it safer and more efficient as well.

We also love the large tank size for this one – meaning you can actually use it on a larger aquarium without having to constantly change the bottle.

What We Didn’t Love

I haven’t seen much wrong with this kit, save the occasional batch of lemons going out to consumers. Overall, it’s a solid product.

Our Verdict on the MagTool CO2 System

For an “all inclusive” kit, the MagTool CO2 system is a great choice for folks needing to inject some CO2 into their aquariums.

The kit comes with everything you need to get started and the system works well over all without a lot of hassle setting it up.

Overall, this is a great choice and worth the (moderately) higher cost for the kit.

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#3. ZRDR


The ZDRD CO2 system is the most comprehensive system of all the ones we reviewed. It comes with literally everything you could need to setup a full system.

The system comes with a 2 liter bottle and all the “fixings,” as well as spare parts, tools, and more.

And, all the professional grade equipment components are stainless steel and built to last.

Here’s the breakdown:

  • Cost effective: Moderately priced – great value for the price
  • Comes with: 2 liter CO2 stainless steel bottle, filter, stainless steel regulator with solenoid, filter cotton, bubble counter, solenoid valve, solenoid valve power supply, solenoid valve connecting line, spare sealing ring, spare atomize piece, 2 snap suckers, check valve, solenoid valve wrench, stainless steel U-tube, stainless steel atomizer, steel bottle base, special air tube, funnel

What We Loved

First off, we love that the kit is as complete as possible in a single, moderately priced package. And when you consider all that comes with, more than reasonably priced!

We love that the components are stainless steel and high quality, professional grade materials.

The 2 liter bottle is a great choice for the most common aquarium sizes, and the equipment runs efficiently, so it’s easy to recommend to most folks.

What really stands out, though, is the bubble refinement. The included atomizer refines the bubbles distinctly so that they dissolve more easily into the water for absorption by plants.

Plus, it’s easy to install and operate and absolutely does all you hope it will do.

What We Didn’t Love

We saw some complaints about the check valves failing or the occasional lemon system going out to consumers.

Overall, not too many complaints about anything else.

Our Verdict on the ZRDR CO2 System

The ZRDR is a great complete CO2 system kit for your aquarium CO2 injection needs. You’ll find all the accessories come with and are made of top quality materials.

The system is easy to set up and use – and the bubble refinement is some of the best on the market.

All in all, this is a top notch choice for anyone looking for a full setup.

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