Best CO2 System For Small Aquariums | Aquascape Addiction

Best CO2 System For Small Aquariums

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We cover what we feel is the Best CO2 system for small aquariums along with some essential Co2 information such as what it does, different kinds and set up information to help you and your tank!

Best CO2 System For Small Aquariums

It is no secret that plants require light and CO2 in order to survive. In fact, those are the two most important components of all. Today we are here to talk about the CO2 or carbon dioxide side of things. You see, plants need to have CO2 and light in order to engage in photosynthesis, which in essence is the way in which plants turn light and CO2 into oxygen, sugars, and the nutrients which the plants need to survive.

In an aquarium, without the right amount of CO2, plants will not be able to properly engage in photosynthesis, thus effectively starving and dying. However, with the right CO2 injection system for a planted aquarium, you can get around this problem with ease.

Let’s take a look at what we think is the best CO2 system for a small aquariums (this is our top pick). We are also going to be going over some other important points of this whole plant and CO2 issue.

What We Think Is The Best CO2 System For Small Aquariums

In our opinion this is the best options for a smaller sized aquariums. It is easy to use, effective, and it gets the job done (you can check the price and more info at Amazon here). Let’s take a detailed look into it’s features, pros and cons.

Fluval Mini Pressurized 20g CO2 Kit

Before we getting into summarizing what the Fluval Mini CO2 Kit, let’s quickly just take a look at the main features it offers.

  • Easy mounting system.
  • Fully pressurized.
  • Regulator valve for control.
  • Comes with a hose and internal CO2 diffuser.
  • Comes with an easily replaceable CO2 cartridge.
  • Ideal for planted aquariums up to 15 gallons.


The Fluval Mini CO2 Kit is a manual CO2 injection system, which means that you need to manually regulate the amount of CO2 being released into the aquarium.

Yes, this means that you will need to keep an eye on plants and fish to see what the oxygen levels in the tank are like. Remember folks, plants need CO2 for photosynthesis during the day when the lights are on. However, during the night when lights are off, plants actually reverse this process and begin using oxygen and creating CO2.

However, as long as you know what you are doing and have a grip on things, this should be no problem. After all, this kit does come with an easy to use regulator valve which you can adjust in order to precisely control the amount of CO2 being injected into the aquarium (you can see more info and pricing on Amazon here). Just to be clear, this particular CO2 injection kit is meant for smaller aquariums only.

Yes, it can easily handle a planted tank of about 15 gallons, a medium stocked tank, but not more than that. If you have a really large tank with a whole lot of plants and a big bio load, you will need a CO2 injection system meant for larger tanks, not this one.

This kit is easy to mount and use, which is an added bonus if you ask us. Some CO2 injectors can be a pain in the butt, but not this one. All you need to do is mount the casing on the side of the aquarium, add the CO2 canister, connect it to the CO2 diffuser, use the valve to control the rate of injection, and you are good to go. In other words, this is a easy to use completely pressurized CO2 system that effectively injects CO2 into your aquarium.

When it comes to small planted aquariums, the Fluval Mini CO2 Kit is a good for many different reasons. It is shown to be tough and durable, it is very easy to use and mount, it lets you precisely control the amount of CO2 being injected, and much more.

All in all, we personally think that this is the best CO2 system for smaller aquariums. There is also the fact that it does not take up too much space in the aquarium, this leaving lots of room for your plants and fish.


  • Easy to use.
  • Easy to mount.
  • Allows for precise control.
  • Fully pressurized.
  • Great for aquariums up to 15 gallons.
  • Space friendly.


  • Requires CO2 cartridge replacement fairly often.
  • Requires you to manually monitor CO2 levels.

You can check the price at Amazon here

How Does A CO2 System For Aquariums Work?

Generally speaking, the function of CO2 injection systems for aquariums is fairly easy to understand. There is really not too much that goes into them. First off, they come with a source of carbon dioxide, which is usually always a CO2 canister, put can also be a small compartment of organic material which produces CO2 as it rots.

Anyway, the CO2 cartridge is the connected to a regulator valve which can be controlled in order to adjust the amount of CO2 being released into the water.

For cheaper models, the regulation has to be done manually, while higher end options come with features that automatically adjust the level of CO2 injection. The CO2 goes into something called a diffuser, which takes the large CO2 bubbles and diffuses them, turning them into miniscule bubbles that can easily dissolve in the water and travel all throughout the water in order to disperse evenly and get to your plants.

Like we said, plants need a lot of CO2 to grow quickly and to thrive, making a CO2 injection system a very important component for a planted aquarium.

Different Kinds Of CO2 Injection Systems

There are 3 main types of CO2 systems for planted aquariums that you need to keep an eye on. Each of these systems has slightly different features and functions in a slightly different way. Let’s talk about the 3 different systems and how they work.


The manual CO2 injection system is the most cost effective version of a CO2 injector for aquariums. The main point to remember here is that they come with a regulator valve which you have to operate manually to adjust when CO2 is released and how much of it is released.

You have to turn it on during the day and turn it off during the night by hand. These use either a small container of decomposing organic matter or a straight up CO2 canister in order to provide your aquarium with CO2. These systems are ideal for smaller aquariums and for people who have time to keep an eye on CO2 levels manually.


These systems are a little harder to install and setup due to an increased amount of components. However, when it comes to their operation, they involve less work for you. These guys usually run on a timer that you can set to your liking. Simply set the timer to turn the CO2 system on during the day and off during the night.

These usually always come with a CO2 canister and a pressure regulator. When it comes to larger planted aquariums with a higher demand for CO2, these semi-automatic injections systems are probably your best bet.

Fully Automatic

Fully automatic CO2 systems are the most expensive and the hardest to properly install. However, once they are up and running, they involve the least work and effort to on your end in order to function. The main difference here is that the fully automatic CO2 systems come with their own pH prober and testing kit.

This means that fully automatic systems constantly monitor the level of CO2 in the water and will automatically make adjustments. Simply set the CO2 level where you need it to be and the fully automatic system will do the rest of the work for you.

If you need help finding a good substrate for your planted tank then checkout this article.

Why Does My Aquarium Need CO2?

Just for a little recap, your aquarium needs CO2 if you have a lot of plants and you want them to grow well. Plants require light and CO2 to engage in photosythensis, the process which plants use to create food and energy for themselves. Without enough CO2, plants can’t live and grow tall as they should. It is as simple as that.

Your tank needs CO2 if it is a planted aquarium. If you have an aquarium with some fish in it, Keep in mind that fish need oxygen to breathe, so you have to find a good level of CO2 diffusion in your aquarium in order to accommodate both fish and plants.

How To Set Up The CO2 System

Ok, so this does differ depending on the type of CO2 injector you have. When it comes to the simple manual ones like the Fluval Mini Kit we covered, the setup process is easy and straightforward. All you really need to do is connect the CO2 cartridge to the regulator valve, connect the tube to the diffuser, put the diffuser in the water while mounting the cartridge on the top lip of the aquarium, and you are good to go.

More complex CO2 systems will require a longer setup process with more parts to connect. However, the setup will be similar to the simpler versions. Your best bet is to just read the instructions on the particular model and make you get for a quick and easy setup procedure.


We hope we have answered some of your Co2 aquarium questions and given you some ideas on what you need. We like the Fluval Mini Co2 Kit and think it has a lot to offer for small aquarium owners (you can check the current price here). There are of course other good options out there, but in terms of ease of use, function, and durability, this is one of the better options. Remember folks, your plants need CO2 and it is up to you to supply it to them.