How to add C02 in small tanks

Setting up a small tank is trickier than it looks and getting the plants to grow can also be difficult.

You only have a small amount of water and aquatic soil to work with and as a beginner it can be frustrating seeing your plants not growing.

There is however a really simple solution to getting your plants thriving – pressurised C02 (carbon dioxide – which plants turn to oxygen and then grow, grow, grow!)

How to add C02 to a nano aquarium

For this guide I’ll be adding C02 to my Fluval Flex tank that was planted out in my setting up a planted aquarium guide.

For this you’ll need to have your tank setup and the following items.

Tropica co2 kit for nano tanks


Setting up the CO2 mini kit

In the box you’ll find the following items – 1 c02 cartridge, tube, holder and a hideous plastic canister for in your tank (you can swap this for a ceramic diffuser if you prefer).

The setup of this system is really easy and the instructions are clear.

  1. Pierce the C02 tank with the nozzle provided, just make sure the valve is closed before you do so. This can be a little tight but you’ll feel it when it goes through.
  2. Take the screw part off and then add the tubing over the tank nozzle, then screw over securing the tube in place.
  3. Place the other end of the tube over the end of the canister where the nozzle sticks out and place in the tank. Tip – fill the canister with water as you put it in.
  4. Slowly (and we mean really slowly) open the nozzle to let the C02 escape – the slower the better! Allow both sections of the canisters to fill with air.
  5. The C02 will now slowly diffuse out of the canister and into the water, you’ll then need to top it back up around twice a day – when the light is going to be on for a while.

Alternatively you can get a ceramic diffuser and just let it run, this looks better but means the C02 needs to be turned off and on with the lights.

Here’s how the setup looks:

C02 canister in a small tropical fish tank

When the canister needs refilling it looks like the below image – It always has a small air lock in the top.

Fluval 20g mini co2 canister when empty

And when full it looks like this:

Canister full of air

Fluval mini 20G C02 review
  • Ease of setup
  • Helping plants grow
  • Looks

Here’s a video guide of me filling the canister in a Fluval Spec tank 

Fluval pressurised C02 comes in larger sizes for bigger aquariums and I personally use the 88G model with a ceramic diffuser in my 190 litre Jewel Trigon corner tank.