How To Make your very own DIY CO2.


Making your own CO2 is very easy and will not take you very long. The four major things you have to look at are, the size and number of bottles you will use, the recipe of course, how to setup the system and how you will diffuse the co2 into the aquarium.
First of all let’s look at the number and size of the bottles you will need. For a 50 gallon aquarium, i use 2x 2L coke bottles which gives me about two bubbles a second, this may not be what you would use with pressurised CO2 but 2bps on constantly is high enough and any higher may lead to a large and unwanted PH swing. For a 25 gallon aquarium and under i would recommend 1 x 2L coke bottle, and then for anything very small probably just a 1.25, but you do not want it to be too small as this will be less effective and need to be replaced more often.

yeast diy co2 bottle make it yourself

Secondly is the recipe. This is what I use and is very effective:

  • Add 2 cups of sugar per 2L bottle
  • Use raw sugar as it is cheaper and contains more complex sugars which take longer for the yeast to break down
  • Fill Bottle to start of neck with warm water (not hot this will kill the yeast otherwise)
  • Add ½ teaspoon of sodium bicarbonate (this will act as a buffer within the water)
  • This can be found in any supermarkets
  • Add ½ teaspoon of vegemite (for those in Australia, apparently it helps the yeast last longer by providing it with a yeast based food)
  • Vegemite is not essential and as stated it is only found in Australia.
  • Add 1/3 of teaspoon of yeast
  • Baker’s yeast is fine but brewer’s yeast will last longer although it may not be worth the extra cost as baker’s yeast will last a fair amount of time
  • After this step put on the cap and shake it until well mixed
  • If done right there should be a slight foam at the top of the water
  • Leave the bottle anywhere from 2-12 hours(unsealed) until it starts to release CO2 and you are ready
  • If it doesn’t begin to bubble the yeast may be expired or the water may have been too hot, make sure you avoid both of these.

bubble counter diy co2

Some tips: Make sure that you only use PLASTIC bottles, there are countless stories of people using glass and the pressure inside has caused it to explode leaving a glass mess everywhere.
How to make the setup:
The best way to connect it all together is to have the bottle caps and drill small holes (just smaller than rubber airline tubing). Push the airline tubing through the bottle caps and glue in with a very strong adhesive such as araldite. If you have more than one bottle, I use T line connectors, they don’t need glue and never fail. It is always recommended to insert an airline valve to stop water being sucked into the setup and keep the pressure high. I use a bubble counter on mine and they can be purchased very cheap, they are very useful to know how fast the CO2 is coming out but also when it’s time for a refill. Next install a pressure release to make sure that if something is clogged, your setup will not explode. Simply insert another T connector and on the third end push in a piece of blutack or plasticine that will pop out in the event of high pressure. From there the airline should go up and into the aquarium, for the next step let’s look at diffusing.

diy co2 yeast in the aquarium

You Can test the levels of CO2 in your tank through a KH/PH chart, these are fairly accurate but it depends how accurate your water test results are

For diffusing DIY CO2 in the aquarium there are a few methods. With pressurized CO2 the best method is use a glass diffuser, unfortunately these get an unknown residue on them that blocks them when using DIY, so they cannot be used. The ‘upside down cup’ method is popular, basically the co2 bubbles out into a small upturned bowl or cup and the contact with the water makes it dissolve, this is good until there is too much CO2 and it cannot be diffused in time. The next and easiest is to inject it straight into the filter intake. This will work as long as the air bubbles don’t congregate at the top and make a deafening noise all the time. The last method is to buy a small water pump and put a very small plastic cup over the out pipe with cloth on its end. Drilling a small hole in the cup and inserting the tubing allows the co2 to flow in, but it cannot escape through the cloth with the water until it is fully dissolved, this is by far the most efficient, more so in fact than glass diffusers.

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