The Purpose of a pH Tester for an Aquarium

Depending on what kind of pH tester you purchase, finding the pH of the water in your tank can be as simple as sticking a digital reader into your water, or combining your water with a chemical and matching the color with a number chart, or dipping a litmus stick into your tank and matching the color with a corresponding number. Monitoring your tank's pH and modifying pH as necessary can help alleviate stress and illness for your tank's inhabitants.

  1. Testing pH

    • The pH tester measures the degree that your water is acidic, neutral or alkaline from a scale of 0 to 14, with 7 being neutral. Optimal pH for your particular aquarium will vary depending on the ecosystem you wish to replicate and the species that inhabit your tank. Fish forced to live in a pH far out of their natural range or fish subjected to rapidly fluctuating pH will invariably suffer from stress and illness.

    The Correct pH for Freshwater

    • Freshwater fish live in waters with a pH from 5.0 to 9.0. The majority of these fish live in water which ranges from 6.0 to 7.5. Optimal pH for your tank will depend on whether your fish inhabit ponds, rivers or lakes in the wild, as well as which part of the world they hail from. As an example, South American discus need water in an acidic range of 4.5 to 6.5, while African cichlids thrive in alkaline water with a pH of 7.5 to 8.5.

    The Correct pH for Saltwater

    • Ocean water generally maintains a pH between 8.1 and 8.4, varying slightly depending on the location. Saltwater fish are very sensitive to pH out of normal range for seawater and are prone to stress and illness from improper pH.

    Rapid Fluctuation of pH

    • An aquarium's ability to maintain pH without rapid fluctuations is known as its "buffering capacity." Maintaining a healthy buffering capacity is important, as steep changes in pH will stress or kill your tank's inhabitants. Buffering capacity is measured as "hardness," or concentration of calcium carbonate, and many pH testers also test calcium carbonate. Aim for a reading of at least 100 mg per liter.

    Raising pH

    • If pH drops below 6, beneficial bacteria that turn toxic ammonia into less harmful nitrates start to die off. Many pet stores sell chemicals designed to raise aquarium pH. More natural methods include using purified tap water instead of distilled or reverse osmosis water, or adding crushed limestone or coral to your substrate or filters. Tanks with high water flow tend to have higher pH levels.

    Lowering pH

    • To lower the pH of an aquarium, you can "soften" the water (remove some of the tank's "buffering capacity," or calcium carbonate) by adding peat to your substrate or filter. Using reverse osmosis or distilled water instead of tap water will lower pH, as does adding driftwood to a tank.