Introduction

In this short article, you will learn the benefits of CO2 in planted aquaria. In addition, we will have a look at three different ways to supply CO2: the popular yeast-based system, the great but more expensive pressurized system, and an original alternative for aquarists looking for a reliable low maintenance system without breaking the bank.

Why should we use Co2 in planted aquarium tank?

Carbon dioxide (CO2) play an important role in plant growth by supplying most of the carbon the plants need. Plants use it to build the basic carbon structures from which all plant material is made and it represents 40% of the plant’s dry weight. Without sufficient CO2, plants cannot photosynthesize and convert inorganic carbon into sugars.

You can grow plants without CO2 supplementation but, if you want vigorous plant growth and luxurious foliage with little or no algae, a good supply of carbon is essential. Under two Watts of light per Gallon, your fish usually supply enough Co2 for the plant to grow but, if the light levels are increased, the growth will be limited by a lack of CO2.
With more than two Watts of light per Gallon, it becomes necessary to increase CO2 because high lighting drives the plants to uptake more CO2 and nutrients. It actually works like a car; the faster you go, the more gas you use. Increasing the lights would have the same results as reducing CO2 and nutrients. It’s all linked together so if you increase one, you must increase the others or you will run out of « fuel ».

Metods of injection

Yeast-Based
The most popular way to supply Co2 is to use a yeast-based system such as the Nutrafin Plant-Gro CO2 Natural System or a DIY system made with a plastic bottle and air tubing.

The bottle is filled with a mixture of yeast, sugar and water. The fermentation of the yeast produces CO2 that goes through the tubing that is attached to a diffuser in the tank.

Yeast-based systems are cheap to buy/build but may cost you more in the long run because you constantly need to add more yeast and sugar (it’s also time consuming).
The other problem with that kind of system is to control the injected CO2 rate and to keep the pH stable. It will supply a good amount of CO2 for a few days (pH will drop) and then supply less and less until the reaction stop (pH will go up).
Your fish cannot adapt to an unstable pH so you risk to lose some of them. Additionally, an unstable CO2 supply will trigger what we fear the most; algae.
The only effective way to provide stable CO2 using a yeast-based system is to use two or more bottles. When the mixture in bottle one starts bubbling slower, it’s time to start a new mixture in bottle two. You might have to do this every 2-3 days.

If you chose to give this system a try, remember that if you squeeze the bottle (even gently), once you release it, it will suck up aquarium water. This can form a siphon and the aquarium water will flood your generator.
Finally, make sure not to use too much sugar or yeast in each bottle because if you do, the mixture may go up the tubing and poison your tank. This recipe works well in containers of roughly 2 liters :

Ingredients :
2 cups sugar
1 tsp baking soda
1/2 tsp yeast (regular dry baker’s yeast is fine)

Pressurized Cylinder
A more expensive method is the pressurized system : A CO2 filled cylinder connected to a pressure regulator. The CO2 goes through a tube attached to a diffuser in the tank.

This system works well because you can adjust the pressure to achieve the desired flow rate. It’s 100% stable and you only need to refill it once every six to 12 month (depending on tank size, planting density etc). To save, you can use a timer to turn the system off at night (plants do not use Co2 at night).

That kind of system is expensive initially but it’s worth the money invested. On the long run, pressurized systems will be cheaper than yeast-based systems and you can expect much better results.

Earth Pellets
Here is an interesting way to supply CO2 to your planted tank. It’s certainly not as good as pressurized systems, but it’s much better than yeast-based systems. I can’t afford a pressurized system for all my tanks so this is what I use for three of my tanks. Plants are thriving!

It works with;
1) A bacteria call Right Now Bacteria,
2) A filtration media call Earth Pellets ..

First of all, the Earth Pellets have a surface area of 980 meter squared per gram which is two to 10 times superior compare to most filtration media on the market.
So more surface area = more surface for the bacteria to establish = more bacteria = stronger nitrogen cycle. That’s simple!

All you need is a canister filter such as a Fluval or Eheim, some Earth Pellets and a bacteria call Right Now Bacteria. Just fill the filter with Earth Pellets and pour in one dose of bacteria.
Right Now Bacteria is so prolific that the Earth Pellets will be fully colonized in one day. I have also read that Right Now Bacteria can be used in some system to complete the nitrogen cycle aerobically and transform nitrogen waste into nitrogen gas (N2)!

Like any living organism, bacteria produce CO2. Unfortunately the average filtration system don’t produce suficient CO2 for plant growth. With the Earth Pellets and Right Now Bacteria, I get a stable 20 ppm of CO2 and my pH went down from 7.5 to 6.5 within the first day. All I have to do now is to rince the pellets once a month. It’s as easy (maybe easier) to use as a pressurized system and cost about the same as a yeast-based system (depending on your tank size).

Conclusion

Those who tried CO2 in planted aquarium can tell the difference. Actually, most don’t come back to non-CO2 planted aquarium once they realize all the benefits of CO2 supplementation.
However, if you’re still unsure but would like to see the results with your own eyes, you can always try Flourish Excel. I don’t beleive it’s a good alternative because it gets really expensive on the long run but it is certainly a great way to see what CO2 can do for your tank.

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