Legend CO2 indicator solution 120mL


  • Safe determination of the CO2 content
  • No need to mix it with aquarium water
  • Can be used in all drop checkers
  • Easy to read
  • Perfect for optimizing the CO2 content of an aquascape



Legend CO2 indicator solution can be filled into any standard CO2 permanent test and serves for the long-term monitoring of the CO2 level in aquariums. An optimal CO2 supply is essential for the thriving of aquatic plants and should therefore be continuously monitored. The advantage of the Legend CO2 indicator solution is that the determination of the CO2 supply takes place independently of the aquarium water, thus substances such as humic acids cannot affect the CO2 check.

Available in a 120 ml container.



The permanent test is filled with 1 – 2 ml of the Legend CO2 indicator solution and then positioned in a well-circulated area in the aquarium. After about 1 – 2 hours, the CO2 content of the aquarium water can be read. A green colour indicates an optimal CO2 supply of approximately  30 mg/l.

A Legend CO2 indicator solution is very useful in an aquarium. Often, aquatic plants lack the essential CO2, preventing optimal growth. With a CO2 permanent test, the CO2 level can be controlled with sufficient accuracy. The dye bromothymol blue used has the property of changing colour in a defined pH range.

CO2 diffuses from the aquarium water through the air bubble in the permanent test into the test solution and vice versa. Depending on its CO2 content, the pH value of the test liquid and thus its colour changes. A defined carbonate hardness in the test liquid determines at which CO2 concentration a certain pH value is established. The Legend CO2 indicator solution turns light green when the pH value is around 6,6. This is achieved at a CO2 concentration of 30 mg/l. For this reason, the Legend CO2 indicator solution indicates a light green tone at a CO2 value of the aquarium water of  30 mg/l. If the CO2 supply in the aquarium is less than  30 mg per litre, the test reagent remains blue; if the CO2 supply exceeds the mark of 30 mg per litre, the test reagent turns yellow.

Additional information

Weight 1 kg
Dimensions 10 × 10 × 10 cm


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