The Aqua Medic CO2 Indicator is used to determine the carbon dioxide content of the water in a simple way. Carbon dioxide is a very important nutrient for healthy plant growth. At the same time, this quite good water-soluble gas is toxic to the animal life in the aquarium in high concentrations so that a check of the available quantity is extremely important. The Aqua Medic CO2 Indicator has to be filled with 1 ml of Aqua Medic Indiactor solution and takes place in the aquarium. A blue colour indicates too little carbon dioxide, a pale green to yellowish indicates too much carbon dioxide. A dark green colour (see indicator disc) shows that the content is okay. If the colour fades in the permanent test, the unit must be refilled.Do you have questions about this article ?