Injecting CO2 into the planted aquaria can be done in one of two ways. The first is employing the use of an expensive ‘professional’ setup and the second – the DIY method using sugar and yeast.
Why CO2?
Plants need CO2 to photosynthesise. In a nutshell; plants need – light of the correct spectrum, fertilizers (whether liquid or substrate), and CO2.
6CO2 + 6H2O (+ light energy) <----->C6H12O6 + 6O2
Lack of CO2 means plants will struggle to grow to their full potential however; it is vital to strike accord between CO2, light and nutrients that are available to the plants. Too little of one will lead to reductions in effectiveness as is shown by the diagram below –
How to DIY the CO2?
Though commonly debated in the hobby, one of the easiest methods is to use a complex chain sugar and yeast. A fermentation reaction takes place and CO2 is produced as a consequence.
The ‘recipe’ so to speak is relatively simple – 2 cups of sugar and 1 (or 1.5) teaspoons of yeast filled to a comfortable level in a 3L juice bottle. It is important not to over fill the bottle as doing so could result in the solution being pushed up the tubing and into the tank! It is good practise to leave about 7cm of space from the top of the bottle to the water line. In the presence of a catalyst like heat, the reaction will speed up. That means that more CO2 will be produced over a shorter time period and thus the end result is that the solution won’t last as long. Cooling the solution will slow down the reaction. Thus it is best to keep the solution at room temperature as far as possible.
Equipment needed –
1 x 3L juice bottle
Adequate length of silicone / CO2 proof tubing (plastic is not advised).
CO2 check valve (better safe than sorry)
DIY rated glass diffuser / ladder / powerhead / filter intake.
Sugar
Activated Yeast
Pliers
Setting it up –
Cut diagonally across a 3cm section of the silicone tubing.
Drill / puncture a hole in the bottle cap that is smaller in diameter than the tube itself.
Insert the diagonally sliced end of the tube through the top of the bottle cap and use a pair of pliers to pull through a 3cm – 4cm section of the tubing. Ensure that airflow within the tube is possible, but there is no gap between the bottle cap and the tube.
Fill the bottle with the sugar, yeast and water. At this point you may choose to add a regulator like baking soda to stabilise the reaction, but it is not necessary.
Leave the tube outside the tank for about 20 minutes while the reaction starts. Then attach your diffuser (or other preferred method of injection) and put the diffuser and tube inside the water.
Water Chemistry with CO2 -
It is important to understand how water chemistry can change with the addition of CO2 to the planted aquaria. Addition of CO2 reacts with the water and will result in the resulting solution being acidic. It is important to make sure that the pH range of your water not drop below pH 4.9 – 5.0; and equally important that the pH stays stable at its level with the addition of CO2.
It is very important to thus have an understanding of KH, GH and their link with pH. Please read this article that provides a comprehensive explanation of the terms.
FAQ –
What do I do if my solution stops producing CO2 far too quickly?
- Adjust the levels of yeast to sugar. Think of sugar as the food, and yeast as the person that eats the food. Too much yeast leads to the sugar being completely consumed and the reaction stops. Too much sugar – while often the safer option leads to a waste of sugar once the yeast gets completely consumed. A little experimentation and tweaks with yeast and sugar levels and you’ll be an expert in no time!
If done correctly (DIY is best used in tanks under 200L) your plants will pearl like this -
The bubbles that are visible on the leaves are tiny oxygen bubbles as explained by the photosynthesis reaction above.