There are 3 ways you can test aquarium water: Strips: strips are chemically pre-coated kits that are easy to use and cheaper. However, they aren’t the most accurate.  Reagents: reagent-based test kits require taking a few ml of water and mixing the reagent with the sample. The final color of the solution determines the parameters. These kits are pretty accurate.  Digital meters: Lab-use digital meters can be used to test aquarium water, but they aren’t generally used due to their cost.