Do All Aquarium Plants Need CO2?

One of the best things an aquarium owner can add to their tanks is plants. By doing so, they can create an underwater landscape that is great to look at and unique.

Besides this, it can do wonders for fish as it is more like their regular habitat and offers them a place to hide should they feel stressed. It can be challenging for a new tank owner to fully understand the ins and outs of adding aquarium plants to their tank.

One of the main topics being the difference in plants, and: “do all aquarium plants need CO2?”

The answer here is two-fold as aquatic plants produce oxygen during the day, and at night this process will be reversed. Depending on the plant types, some tank owners inject CO2 into the tank as it helps enhance size and color. Besides this, there are low energy tanks where plants don’t require additional CO2 and are much more comfortable for new aquarium owners to establish.

Aquarium CO2

CO2 and Aquatic Plants

Like fish, plants require care, and much of this can come in the way of various fertilizers, yet also with ample amounts of CO2. Without CO2, your aquarium plants won’t carry out photosynthesis, which will inhibit plant growth.

CO2 is the primary nutrient that enables the growth of your aquarium plants. On most occasions, they can suffice with what is naturally released by fish and bacteria in your tank.

This does, however, fall on aquarium plants that are in the categories of Medium and Advanced.

In a low light aquarium, the addition of CO2 may not be required as there is less stimulation for aquarium plants to grow under such low levels of light. In this scenario, plants can obtain sufficient CO2 from surface agitation, breakdown of organic matter and fish respiration.

Fertilizers and Aquatic Plants

Besides CO2, plants require nitrogen (N), phosphorous (P), iron (Fe) and manganese (Mn).

You find these referred to as macronutrients, and because plants require relatively large amounts, your aquarium plants can absorb these macronutrients through leaves and roots. Because of this, you can add said fertilizer using two distribution methods.

First is as a fluent fertilizer, which you add to the water. Second, is as capsules you add to your aquarium substrate.

Adding to the water requires regular doses that can be daily or weekly, and it can lead to over fertilization and problems with algae problems. You find this when plants are unable to absorb fertilizer as you add new doses.

The problem here is that it can be the only way to add fertilizer to moss, floating plants, or plants on rocks or a tree root since the roots are not located beneath the substrate.

Using nutrient capsules is suggested for large, sturdy plants and can release nutrients over several months.

Fertilizers and Aquatic Plants

Energy in Aquariums

When you have a planted aquarium, they will offer different energies. You find this comes from the lighting you have.

High-energy tanks will be those, which are brightly lit and require strong water flow, lots of CO2 and the inclusion of daily fertilizer and lots of water changes.

A medium energy tank will comprise medium lighting levels; there is less need for CO2 and fertilizers and far fewer water changes as there isn’t as much photosynthesis occurring.

Low energy tanks require less lighting, fertilizer, water changes and no additional CO2. In these tanks, plants grow far slower. One of the advantages of these low-level aquariums is the setup, and running costs are far less than others.

Aquariums Without CO2

It can be challenging and costly to maintain a tank that requires CO2 injection to keep it healthy. Low energy tanks are the best option to have plants and let them grow at a natural, but somewhat slower pace.

Here are a few of the things you need to think about should you wish to have a low energy planted tank.

Aquariums with and without CO2

Tank Lighting

For a low energy plant tank, regular stock lighting is adequate. Because of this, if you have tanks from Fluval, Tetra, Evolution Aqua, or Juwel, the lights offer suitable output to get started.

As many tank owners perceive, light is the most essential aspect for any plant, and there is the thought that adding more will benefit plants. However, with an increase in light, you increase your plants’ metabolic rate, and thus they need more fertilizer and CO2.

Suppose you have a bright light and don’t adjust the other two sections of the triangle accordingly; algae issues will be the result.

While the light levels will be lower, this doesn’t mean your plants can do without. All underwater plants still require the right amount of light, which should be around 8 – 10 hours per day.

The difference will be in the output your bulbs have, and often the reason why kit lights make them ideal for low energy tanks. Besides this, creating a day and night cycle is essential so your plants can carry out photosynthesis as they need to.

Tank Substrate

When you have a CO2 free aquarium, you need a substrate that will be as nutritious to your plants as is possible. You can use aquatic soils on their own, or you can add a layer of substrate fertilizer beneath a gravel layer.

Fertilizer balls can be used where you insert these in the gravel. With either substrate, you need to make sure your soil or gravel layers have a minimum depth of 2-inches.

Aquarium Fertilizer

Plants in a low energy tank have far fewer nutrient requirements than those in medium or advanced tanks.

However, they still require a full range of nutrients you can add for premium liquid fertilizers. You will add these after a weekly water change or split weekly doses by a factor of 7, and add daily.

Filters in Low Energy Tanks

You can discover that your water flow in a low energy tank is very low. Because of this, you can use an external canister filter that you can place out of sight. It is also an option to use filters that come with built-in heaters.

Plants for No CO2 Aquariums

When searching for plants, you will find these fall into the easy, medium and advanced categories.

You will need to select from the easy range of aquarium plants when building a low energy aquarium as the CO2 requirements will differ.

You will find you don’t have to miss out on any of the best underwater plants as you can still select from:

  • Anubias
  • Bacopa, Bucephalandra
  • Ceratophyllum, Cryptocoryne
  • Echinodorus, Hygrophila
  • Lobelia, Ludwigia
  • Microsorum, Sagittaria, Staurogyne
  • Vallisneria

You can find many more besides these, yet the same steps you need to take will be the same for any.

Please select the right aquarium plants for your tank, make sure they are strong and healthy and free from algae when you purchase them.


Be sure to fertilize regularly, and keep your light levels to a minimum. Once you follow all this advice, you will find you can have a great looking underwater plant-scape that doesn’t require any additional CO2.