CO₂ is one of the most important nutrients for aquarium plants. At the same time, too much CO₂ can hurt other organisms of the aquarium. For this reason, long term monitoring of the CO₂ levels in the aquarium is highly recommended. After inserting a CO₂ reagent into the CO₂ Drop Checker and placing it in the aquarium, the color will change according to the concentration of dissolved CO₂ in the aquarium water. Green indicates a proper CO₂ value, yellow indicates too much CO₂ and blue shows CO₂ not enough.

Please note that the required CO₂ Drop Checker reagent is sold separately and does not come with this glass CO₂ Drop Checker.