How To Setup CO2 For Aquarium: Guide | Aquascape Addiction

How To Setup CO2 For Aquarium: Guide

As an Amazon Associate I earn from qualifying purchases.

If you need help setting up Co2 for your aquarium then look no further, this article covers what items you actually need and a very detailed step by step setup guide to ensure you do it the correct way for proper plant growth.

How To Setup CO2 For Aquarium: Guide

If you have planted aquarium with lots of aquatic plants, you probably know all about CO2. When it comes down to it, CO2 or carbon dioxide, is the number one most important thing in terms of the survival of your plants.

All aquatic plants, as well as all land based plants, require CO2 for respiration, photosynthesis, growth, and ultimately to live. When it is light outside, plants engage in photosynthesis to turn water and CO2 into sugar and oxygen which they use to grow.

If we are talking about nature, the CO2 needed by the plant comes from the medium which they are rooted in. However, an aquarium usually does not have enough CO2 within the substrate to enable good plant growth, especially in large quantities. There is not much plant decay in an aquarium and the water you put in the tank also does not have much CO2 in it. Therefore, you need to find a way to inject CO2 into the aquarium to enable proper plant growth.

If you want your planted aquarium to be as successful as possible, we would definitely recommend always injecting CO2 into it. CO2 is absolutely necessary in tanks with high levels of light, because the more light there is, the more the plants are engaging in photosynthesis, which means they need more CO2. For a low light tank, CO2 might not be completely necessary, but it will still help with overall growth. At any rate, let’s now talk about what you are going to need and how to setup CO2 for aquarium plant growth.

The Items You Will Need For CO2 Injection

There are quite a few different items that you will need to purchase for proper aquarium CO2 injection. This is especially true if you have a large aquarium with a lot of plants and need to supply them with plenty of CO2 (We have covered our top pick for smaller aquariums on this article). Now, there are some all in one CO2 injectors that you can buy, which come with everything you need.

However, these tend to not be the best choices around. Either way, whether you buy an all in one CO2 injector or not, here are the different components that you will need for full and proper CO2 injection into your aquarium.

The CO2

Ok, so the first thing that you are going to need to get is the CO2 itself. CO2 is going to come in a pressurized bottle. These can come in different sizes, so you need to figure out which size is best for the aquarium that you have.

Most people would recommend getting a large CO2 bottle. While they are more expensive to begin with, they are cheaper to fill up in the long run and they will last much longer too.

The Regulator

The next thing that you are going to need is a regulator. The problem with CO2 bottles is that there is immense pressure contained inside of them. If you were to puncture a hole in one, they would pretty much blast all of the water right out of the tank.

The regulator works to decrease the pressure to control how much CO2 is being released in a given amount of time. A CO2 regulator gauge for precise control is recommended as well.

A Solenoid

A solenoid is a good thing to get because it will automatically turn off the CO2 when it is no longer needed. Plants do not require CO2 when the lights are off because they do not engage in photosynthesis in the dark.

You can actually turn the CO2 off about 1 hour before you turn the lights off because there will be enough CO2 remaining in the water for that hour. Anyway, you cannot always be there to turn the CO2 off, so a solenoid is convenient because it does the job for you.

The Bubble Counter

Simply put, the bubble counter is used to measure how much CO2 is being injected into your aquarium at any given time. You will use the bubble counter to measure how many bubbles are being sent into the aquarium per second. You can then use this measurement to determine whether more or less CO2 is needed.

The Diffuser

A diffuser is one of the most important parts of the CO2 setup. The CO2 bubbles, as they come out of the bottle, are too large to be effective. They would more or less float right to the top without really mixing in the water. The CO2 diffuser turns the large bubbles into very small bubbles that can easily diffuse right into the water.

The Tubes

Make sure that you get specialized CO2 tubing because normal air line tubing will simply not do. Simply put, you need tubing to connect the various components of the CO2 injection system, mainly for connecting the regulator to the diffuser.

A Drop Checker

Now, this is not totally necessary, but a drop checker definitely helps. This is a special little tool that you can use to measure the amount of dissolved CO2 in the water.

How To Setup CO2 For Aquariums The Right Way

Setting up this CO2 system is really not that hard. You can look up any CO2 injection system diagram and they are all pretty much the same. It really only takes a few minutes to set the whole thing up, which is always nice.

Let’s go through a simple step by step process on how to set up CO2 for your aquarium;

  1. Use your spanner to connect the regulator to the CO2 bottle.

  2. Attach the solenoid to the regulator.

  3. Using the CO2 tubing, attach the solenoid to the bubble counter.

  4. Using the tubing, attach the bubble counter to the diffuser.

  5. Mount the diffuser in your tank near the bottom.

  6. Plug in the solenoid and set the timer in order for precise CO2 release.

  7. When you have everything put together, open the needle valve a little bit on the regulator before opening the bottle to release has. This will help avoid certain components from being damaged.

  8. Now it is time to switch on the main valve on the CO2 bottle in order to release the CO2. If the bottle is full, the gauge on the regulator should read between 800 and 1000 pounds per square inch of pressure.

  9. Now you need to open the needle valve slowly until you see bubbles coming through the bubble counter. Using your needle valve to regulate the speed of CO2 release, try to aim for 1 to 2 bubbles per second, which you will see in the bubble counter. Make sure to only move the needle valve by very small amounts because they are quite sensitive. A little bit goes a long way.

  10. Using the drop checker, for the first few hours after you turn it on, measure the amount of CO2 in the water and make the according adjustments depending on your needs. Keep in mind that it takes a drop checker roughly 1 hour to react, so whenever you look at the drop checker, remember that it is indicating what the CO2 level in the water was like 1 hour prior.

  11. If you like, get yourself an electric timer plug for the solenoid. This way you can control exactly when CO2 is being release into the water and when it is not.

Some Other Quick Tips

Here are a few tips in terms of CO2 injection that you can follow to ensure the optimal growth of plants in your planted aquarium.

  • Always have the CO2 turn off around 1 hour before the lights go out. There will be more than enough CO2 in the water to last until the lights go out.

  • Have the CO2 turn on around 1.5 hours before the lights go on. This will ensure that there is enough CO2 present in the water as soon as plants begin photosynthesis.

  • Keep in mind that all tanks are a little different, so you might have to experiment a little bit and engage in some trial and error before you get things right. This is especially true in terms of the times at which you turn the CO2 on and off, as well as with the bubble counter.

  • If you have fish in the tank, make sure that you do not inject too much CO2 because it will lead to breathing problem and potentially the death of your fish. You should probably get the CO2 levels right before you add fish to the tank.


We hope that we have been of help here. Remember folks, planted aquariums always do better with CO2 injection, so if you want nice, big, and healthy plants, this is something you will want to do.