Testing the pH of your aquarium water regularly to make proper adjustments is crucial to keep your fish, plants, and other aquarium animals healthy and stress-free. pH is the measure of acidity or basicity of liquids. Acidic water will measure between 0 and 7 pH, while basic, or alkaline, water will measure between 7 and 14. Knowing your animals is important: the preferred pH range of each species in your aquarium can vary.

A consistent pH reading is more ideal than frequent changes up or down. pH is influenced in the aquarium by many factors, including the KH content, respiration, organic waste decomposition, even the ammonia cycle. Because of this, frequent testing is recommended. Established systems should be tested once a month, and new systems or aquariums with fish illness or death should be monitored more often. Establishing a baseline pH of your aquarium throughout your normal routine will help alert you to problems early on. Any unexpected pH change can indicate water quality issues and should be addressed right away.