In order for fish to thrive, water must be similar to that which could be found in their natural environment. Poor water quality can cause fish stress, illness and even death. Regular testing of the water is crucial, particular with a new aquarium, in order to keep parameters like Ammonia, Nitrate, and Nitrite in check. High levels of these can cause poor fish health or death, and may be a sign the filtration is not working efficiently. Liquid test kits, although looking a bit like something from a science lab which could be intimidating they are actually very easy to use and provide very accurate results.