JBL ProAquaTest CO2 Direct RefillSimple and safe monitoring of aquarium water parameters. Determination of the optimal carbon dioxide content in freshwater aquariumsUse: fill the plastic test tube with water to be tested, add the reagent drop by drop until stable pink coloring. Number of drops x 2 = CO2 content in mg/lUse in case of no or poorly growing plants or dead fish: once a weekOn the JBL website/Aquarium topics you will find detailed information about water analysis and problem solutions.Contents: 1 quick CO2 test, 2 reagents, plastic test tube and color chart. Reagent refill available separately.