Dennerle CO2 Visual Indicator -
Provides a long-term accurate indication of CO2 level in aquarium.
Mode of operation: CO2 is a very volatile gas. It diffuses through the special diaphragm on top of the test container. There it diffuses more over the air gap into the indicator solution. The CO2 Visual Indicator has a particularly fast reaction, both for higher and lower pH values.
Technical data: YELLOW = too much CO2 / GREEN = right CO2 level / BLUE - too few or no CO2
For freshwater aquatic plant aquariums and ponds