Here is what you will need:
- 1 plastic bottle of any size with the fitting cap, 2 liter soda bottles are popular and effective.
- 1 Electric drill, this can be replaced with a hammer but will not be as efficient.
- 1 Drill Bit (or nail if you are choosing to use the hammer), Be sure the bit/nail is slightly smaller in diameter than the airline tubing.
- Several feet of airline hosing, most if not all types will work fine.
- One tube of Aquarium safe silicone.
- Pliers, may not be needed.
- 1 pack of Baker's yeast.
- 2 and 1/2 cups of sugar.
- 1 tsp. of baking soda.
- Luke warm water.
Step 1: Get the drill and bit ready, along with the bottle cap. Make sure to drill on a surface that is allowed to get damaged in case you accidentally drill too far. Place the bottle cap on the work area so that the top is down, this will keep the top from cracking in case you apply too much pressure. Carefully drill a hole in the center of the cap. If you are using the hammer and nail, place the cap as instructed above. Place the nail in the center of the cap where the hole will be. In one strong and sturdy swing with the hammer, hammer the nail through the cap, making a nice hole for the hosing to fit through.
Note: the hammer and nail method are much less effective and run a greater risk of making an error than using a drill to create the hole.
Step 2: Take the scissors and airline tubing and cut the airline hose at a slant near the end so that it is pointed, this will make it easier to pull it through the small hole in the bottle cap. Push the pointed tip of the airline hosing through the hole, if needed grab it with the pliers and pull it through (it should be an extremely tight fit) . Don't worry about mangling the airline hose, you can always pull it through more and cut off the section of disfigured hose. Take the silicone and apply it around the airline hosing on the cap to create an airtight seal. Use it very sparingly on the inside as too much may affect how the bottle will screw on. Allow this to sit and cure for the time indicated on the silicone package (usually 24-48 hours).
Note: Do not cut the hose to length yet, there are few things worse than have a hose that is too short.
Step 3: Test the seal by screwing the cap onto the bottle and blowing as hard as possible into the hose. Listen for leaks, if any are present, remove the silicone and reseal it.
Step 4: Next up is to mix the recipe. Take your bottle, and pour 2 and 1/2 cups of sugar into it (you may save yourself some frustration and some time by using a funnel). Add 1/2 a tsp. of baker's yeast. Add 1 tsp of baking soda. Fill the bottle with luke warm water until it is 3/4 full. Shake the mixture very well.
Step 5: Screw the bottle cap onto the bottle making sure it is tightly fitted. Take the airline hose and attach it to your method of diffusion. This is a good time to cut the hose to length.
Step 6: Shake the mixture well every few days to ensure to keep the mixture going strong consistently and to keep any undissolved sugar from settling in the bottom of the bottle. After the mixture's CO2 production has slowed considerably, it is time to empty it and mix up a new batch of mixture. Simply follow the instructions again, making any adjustments that are needed to suite your situation.
This recipe is only what has working for my systems, I recommend altering this recipe to accommodate your needs or preferences while taking the following into consideration. The amount of yeast that you mix into the recipe will effect the speed and amount of CO2 that is put out, but this will mean that length of time it lasts for will decrease as it will intake the sugar much faster. On the other hand, mixing less yeast will result in slower CO2 production but it will last much longer. The amount of sugar mixed is a determining factor in the length of time that it will take for the mixture to run out. The more sugar, the longer it will last, the less sugar the shorter its life will be. Of course, there is a limit to the amount of sugar that can be dissolved into the mixture, so after a certain point, adding more is just a waste and won't make much difference. Therefore a balance between the amount of sugar, yeast, and what your needs are must be made to ensure that you get the most out of your mixture.
Diffusion is one the most important aspects of this DIY project. Irrelevant of the amount of CO2 your mixture is creating, without an effective method of diffusing the CO2 into the water the mixture will be wasting precious carbon and will not be very effective in aiding your system. There are several ways of diffusing the CO2 into your water, all ranging in effectiveness and complexity. My personal favorite method is to attach the hose to the intake of a filter or power head, this way the Co2 gets sucked in and mashed into hundreds of tiny bubbles that can then be dissolved, creating a very effective way of diffusing. I like this method because of its simplicity, its effectiveness and for the fact that it can easily be hidden from the casual observer. Other methods include complex and simple reactors that keep these bubbles in contact with the water for longer periods of time until they can be completely dissolved. Although these methods are more effective, they can be difficult to create and manage. Other ways are pumping it through air stones or commercial glass diffusers to create tiny bubbles. Both are effective, the latter being the most effective method. I plan to discuss these methods of diffusion in future articles.
In conclusion, this recipe will provide you with the ability to create and diffuse CO2 into your aquarium. As stated above, you may need to alter this recipe to fit your needs or preferences and to match your selected method of diffusion.