The Fluval pH Wide Range Test Kit for Aquarium Water, Freshwater & Saltwater Fish Tank is a must-have for any aquarium. This kit contains 100 pH tests, so you’ll have plenty to use for all your fish species. The pH of water is one of the most important parameters to measure because it affects numerous biological processes. It’s recommended to test the water weekly in order to chart changes that can affect the well being of your fish.