Why DIY?

Pressurized CO2 systems are an expensive investment. You may not be sure it will be worthwhile, and would like to try CO2 injection to see how it affects plant growth before spending the money for a pressurized system. Or maybe you have 3 tanks in 3 different rooms, which would require 3 pressurized systems. Perhaps you are on a student budget and just can't afford a commercial system. Or maybe you have a 50 litre tank and figure a full CO2 system would be overkill.

For any of these reasons, a DIY CO2 setup would be worthwhile. It costs very little, can be set up in a single day, and only requires a few minutes of maintenance every few weeks. And the difference to your aquatic plants can be dramatic.

So How Does It Work?

A yeast culture is started in warm sugar-water inside a closed bottle with tubing leading into the aquarium. As the yeast begins to reproduce and metabolize, it uses the sugar for energy and begins to produce CO2 as a byproduct. The CO2 builds up a slight pressure inside the bottle and then exits through the tubing into the aquarium. Various diffusers and reactors can be used to disperse the CO2 throughout the tank. The yeast culture continues to produce CO2 until all the sugar is used or until the alcohol level in the bottle reaches toxic levels.

How Do I Set Up a System?

You will need a 2L Fizzy bottle or plastic container with a screw cap which fits tightly, some standard airline tubing, and silicone glue from the hardware store.

Drill or punch a hole into the bottle cap to the approximate size of the airline tubing.I find that if you make the hole slightly smaller than the tube,it creates a tight fit and silicone is not required. Insert the tubing so that it extends 2 to 3 cm into the bottle cap. Glue the tubing to the cap on both inside and outside. Allow to dry overnight. At some point on the tubing, insert a check valve so that gas can exit the bottle but not return. This will prevent any siphoning from the tank into the bottle.

RECIPE: Using a funnel or rolled up paper, pour 2 cups of sugar into the bottle. Add 1/4 teaspoon of baker's yeast and a pinch of baking soda. Pour in a little warm water (NOT hot) and mix around to dissolve the sugar and yeast. Then fill to the shoulder (just above the label on a soda bottle) with warm water. Shake well and cap with the tubing-cap assembly. Run the other end of the tubing into the aquarium.

This setup will serve an aquarium in the 30-150litre range.

To disperse the bubbles, you can do any of the following:

- place the tubing into or under the intake to the canister, powerhead or power filter, allowing the filter impeller to disperse the bubbles. Caution - do not place the tubing in any high flow area which might create a vacuum in the tubing and collapse the culture bottle or siphon the culture into the tank!

- place an airstone on the end of the tubing and anchor in the aquarium.

Yeast mix usually will last for two to three weeks and with the occasional swirl will continue to produce sufficient CO2 bubbles for lush growth of plants.

REMEMBER: you will need more than just CO2 to grow plants

Also required are LIGHT and NUTRIENTS

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.

place an airstone on the end of the tubing and anchor in the aquarium.

I have been told that airstones will get clogged, causing a buildup of CO2 gas, resulting with the bottle exploding. Pollen Glass CO2 Diffusers are much better, as they are specially designed for DIY CO2 systems.

http://img216.imageshack.us/img216/3457/nano1rb2.jpg

Perhaps mods can combine both Supasi and P44's posts into one sticky?

We are looking into doing that 8)

We are looking into doing that 8)

More like you are waiting for me to do it because you cannot remember how to ?

Saturday afternoon... what to do?... Got inspired by the talk about DIY CO2.. thought: "I can do that!"

The bottle:

And my temporary improvised diffuser:

How long before the water goes that colour? Mine is still opaque...maybe I should put in more yeast??

How long before the water goes that colour? Mine is still opaque...maybe I should put in more yeast??

I used brown sugar... read a bunch of places that it worked better then normal sugar.. hence the colour.

:lol: @ Zev. How did you guess?? :roll:

I used brown sugar... read a bunch of places that it worked better then normal sugar.. hence the colour.

Damn, will it still work ok with white or have I just wasted 2 cups :oops: .

Will work with white, and you can always try brown when your mixture needs replacing in a few weeks.

Will work with white, and you can always try brown when your mixture needs replacing in a few weeks.

Phew! Will do thanks

Wow!... it dropped my pH from 7.2 to 6.2 in 4 hours!..

Hope it won't keep dropping

Hmmm... the perils if not being able to regulate the C02 that goes into your tank.

Hmmm... the perils if not being able to regulate the C02 that goes into your tank.

True... I tested again this morning and it was around pH 6.0.. I think it has stabilized now.. It's the Amazon community tank so 6 is ok.. fish seem happy as ever..

Question: I usually do a large WC of 40-50% every week.. my tap water is pH 7.2-7.4.. Would my fish get a shock if I do that now?

Would DIY work in a larger tank - say 500l, if I set up two separate systems independant to each other at opposite ends?

Would DIY work in a larger tank - say 500l, if I set up two separate systems independant to each other at opposite ends?

Depends on the size/output of said systems. Bottles containing the mixture (in theory) can be any size. Should be able to up scale it all, please tell me if you find some 30L bottles

So after setting this up (thanks for the guide Supasi and P44) my pH has gone from 7.2 to 6.0

Will this be a problem when doing water changes? I mean my tap water is around 7.4 and I usually do 50% per week.

Is there a direct correlation between % water changed and pH? eg. if I do 50% will pH end up on 6.7? and is this too big a shock for the fish? (discus, cardinal, corys)

Thanks

I don't forecast it being a problem at all... but time will tell I suppose. I'd be confident in doing the 'normal' WC that you do.

I don't forecast it being a problem at all... but time will tell I suppose. I'd be confident in doing the 'normal' WC that you do.

Excellent!

If my fish are floating belly up in an hour I will report back

Ok my discus was NOT happy with pH going from 6.0 to 6.7 in one water change... They all went completely black and went into hidding.. they are usually quite inquisitive during WC..

So the co2 production came to a halt after only 4 days! I followed P44's recipe of 2 cups sugar and 2 teaspoons yeast.. but after googling other recipes found that most recommend 1/4 - 1/2 tsp yeast to two cups sugar. this would explain the massive production of co2 - low pH - and only 4 day duration.

So I've made a new batch with only 1/2 tsp yeast (as Supasi recommended) and hope that will last longer and not drop my co2 so much..

As P44 wrote it's definitely about tuning it in to your setup..

Add some calcium to the tank.

I grow some swords in my tank and have a layer of shells at the base of my substrate for them.

Undoubtedly that helps buffer the water.

Thankfully you tweaked the CO2 based on your tanks requirements. Is there a certain aspect of my post you would like me to edit?

Two tea spoons of yeast is too much in my opinion. You will end up with a rapid increase in CO2 production and then it will die off as the alcohol kills the yeast.

Start with 1/4 to 1/2 teaspoon and the co2 production is more constant and does not die off as fast. This prevents the rapid spikes in PH.

Think of the story of the hare and the tortise. Slow and steady wins the race

I found that on mine the 2 teaspoons was far too much and I've gone back to half a tea spoon. All good though - it now lasts 3 weeks or so without refilling.