Carbon dioxide

Carbon dioxide 

Also called Carbonic acid gas, Carbonic anhydride, dry ice (when solid).

This is a gas given off by all plants at night. is absorbed by plants during photosynthesis.


 * when mixed with water becomes carbonic acid.


 * dissolves quite easily in water but is also easily removed by water agitation.


 * If you wish to grow plants well in an aquarium you may need to add to the water.

It is often considered that a value of 15ppm is required in the aquarium to grow plants successfully.

Measuring in your tank
There are several methods of measuring the level of carbon dioxide in the water.


 * The most popular way is by the measurement of the pH and KH values of your tank water then you can find out the level of dissolved by reading from a graph.  This method will yield inaccurate results if there are any acids other than carbonic acid in the water.

Graph

 * Excel Spreadsheet of Chart is available here.

This glass bubble contains a small amount of liquid chemical (a 4 KH reference liquid containing Bromothymol blue) and you place in it a few drops of distilled water and then submerse it and attach it to the inside of your tank. The liquid turns either blue for too little, green for the ideal amount and red too much. One end of the bubble is open to the water and so in the water disperses slowly into the chemical therefore displaying the colour. (Process takes about 60–120 minutes).
 * By the use of a glass bubble (also called a  indicator or  bubble tester) submerged under water.
 * Note don't place aquarium water in the bubble if you have high phosphate levels or wood in your aquarium as these lower the pH and therefore will lead you to read higher levels of than there are in the water.



There are many of these test kits on the market. Some of these kits use the pH-KH relationship described above and so are subject to the same inaccurate readings if acids other than carbonic acid are present in the tank water. See The Krib on Test kits for more information on how they work.
 * By using a commercial test kit.


 * See testing article.

Links

 * Wikipedia on
 * DIY Systems by John LeVasseur
 * The Krib on
 * DIY using Yeast
 * in the Aquarium
 * Pressurised system
 * A Treatise on DIY Systems
 * Checker with 30ppm reference


 * Read the Yeast article. and its links for CO2 generation using Yeast.