Do You NEED CO2? – Why, When, and How

Do You NEED CO2? – Why, When, and How


In this article, you will learn why CO2 injection is neccessary for planted aquariums, and when you should be using it

When you think of growing plants; the common or average person will likely assume all thats needed for plants to grow is Light, and Water. While that is the case, they are missing 1 Key Ingredient; CO2

There are 3 Key Elements to growing any sort of plants whether they are aquatic, or terrestrial plants; Light, CO2, and Water.
While there are also other neccessities for plants to grow, like plant food or fertilizers; we will not be discussing it today in this article. This article will hopefully provide you enough information to make an educated decision, on whether or not you require CO2 for your Aquarium.

Basic Photosynthesis

Photosynthesis is a process plants undergo during the day when they receive their main source of food or energy; Light. Every plant needs light one way or another, some plants are less demanding than others and don’t need as much light.
From our experience, most aquatic plants only have a photo-period of 7-9 hours; some people may tell you a little more, or a little less; keep in mind everyones aquarium setup is different, utilizing different equipment, different tank sizes, etc. What works for you, may or may not work for someone else.
During the photoperiod, plants will need to consume or absorb carbon dioxide which is an unlimited resource when it comes to terrestrial/land/air plants. CO2 is naturally in our air, it’s apart of our lives and we breathe it in on a daily basis.
When it comes to aquatic plants however- In nature, CO2 is naturally created in the enviroment above and inside the oceans or lakes. However, CO2 is not easily contained in home aquariums, and in most cases- must be injected when keeping demanding aquatic plants.

Which Plants Require CO2?

To put it short and simple- all plants will “require” CO2 one way or another to live. CO2 will make any plant thrive and grow much better. Home aquariums will usually have a very low amount of CO2 in the water naturally already. The image below depicts the prime example of how aquatic plants will look with and without injected CO2.


Some questions you might want to ask yourself is;
1. Are you trying to grow High CO2 Demanding plants?
2. Do you want fast plant growth?
3. Don’t want to wait over 6 months for carpetting plants to fill in?

If you answered yes to atleast 2 of the questions above, you may want to consider CO2.

However, there are a handful of plants that will do fine without CO2, they will just grow at a much slower rate and not as bushy or filled in.

Here are some recommendations on plants we sell at Planted Aquaria that do not require CO2.

Epiphyte Plants (Recommended to glue or tie onto a decor, rock, or wood. DO NOT plant in the substrate or they will die).
1. Anubias Species
2. Bucephalandra Species
3. Java Fern
4. Moss Species such as, ‘Christmas’, ‘Flame’, ‘Weeping’, ‘Spiky’, ‘Taiwan’.
5. Bolbitis heudelotii
6. Hygrophila pinnatifida

Stem Plants
1. Limnophila Sessiliflora
2. Rotala rotundifolia
3. Ludwigia Palustris or Rubin
4. Hygrophila- corymbosa ‘Siamensis 53B’ | polysperma ‘Rosanervig’ | corymbosa

Rosette Plants
1. Amazon Sword
2. Cryptocoryne wendtii ‘Green’ or Cryptocoryne beckettii ‘Petchii’
3. Echinodorus ‘Ozelot’

Carpetting Plants
1. Sagittaria subulata
2. Vallisneria Spiralis
3. Marsilea hirsuta
4. Helanthium ‘Green’ or Helanthium ‘Quadricostatus’
5. Micro sword a.k.a Lilaeopsis

How to Set Up CO2

There are multiple methods to inject CO2 into the aquarium water. Keep in mind, at Planted Aquaria we currently have only a couple system options, and we are always considering bringing in more great options for our customers.

OPTION #1 – Low Initial Cost / Expensive Longterm
$39.99 Aquario NEO DIY CO2 Kit System
$22.99Aquario NEO DIY CO2 Refills
Aquario’s solution for low cost CO2 system is definitely refreshing to see. While initially the cost is low, this system will only last about 2 months on average, and you will need to buy the refills for $22.99 from then on. It includes everything you need to start with CO2 injection, such as CO2 Tube & Diffuser.

OPTION #2 High Initial Cost / Cheap Longterm
$109.99Certified 2.5lb CO2 Cylinder (CO2)
$169.99CO2Art Pro-Se Dual Stage CO2 Regulator (controls the CO2)
$14.99CO2Art Precision Check Valve (Prevents water from back siphoning into regulator)
$30.99-$48.99Diffusers (Different sizes depending on styles and tank size)
While this option may seem hefty initially, a 2.5lb Cylinder usually lasts anywhere between 10-12 months for a 5-10 gallon aquarium. You can of course, choose different Cylinder sizes, they come in 2.5lbs, 5lbs, 10lbs, and 20lbs. Once you set a Cylinder up, refills at a local brewery should cost anywhere between $20-$30.


So let’s do the math for 3 years of CO2 injection for both systems and see what they ultimately cost at the end.

OPTION #1 (Aquario DIY CO2)
Initial Cost– $39.99 (lasts 2 months)
Refills for 34 months – $22.99 x 17 (assuming each refill will last 2 months)
= $390.83 for 3 years.

OPTION #2 (CO2 Cylinder)
Initial Cost – $324.96 (Lasts 10-12 months)
Refills for 3 Years – $24.99 x 3 (Assuming refill price and 1 year)
= $399.96

In conclusion; if you plan on setting up a CO2 Planted tank for more than 3 years. We highly recommend you go with OPTION #2 (CO2 Cylinder). After 3 years, the cost will be cheaper because it will only cost around $25 for a refill every 10-12 months vs buying refills every 2 months.

If you are simply just trying out CO2 to see if it is for you, and unsure if it is something you want to stick with entirely, OPTION #1 (Aquario DIY CO2) Is the best option.

Written by Tom Tran
Planted Aquaria