What Is the Meaning of the pH Balance in Aquariums?

Water is to fish what air is to humans. Neither air nor water must maintain an exact mixture of its chemical contents to sustain life, but way too much or way too little of certain things can cause illness, or even death. Each fish species has a preference as to the amount of ammonia, nitrates, nitrites and hydrogen it can tolerate. As far as hydrogen is concerned, there are two key factors necessary for a healthy aquarium: having the appropriate levels for the fish involved and keeping those levels stable.

  1. Definition of pH

    • Natural waterways maintain their own pH balance.

      Chemically, pH is a measurement of the concentration of hydrogen atoms in a solution. An acid solution has a pH of 0, and an alkaline solution has a pH of 14. A pH of 7 is considered neutral. While they may do well within a limited pH range, most fish kept as pets can't survive extreme fluctuations in the pH level of the water. Also, some species require a more specific pH to spawn than others.

    Factors That Affect pH

    • Decorations become part of the aquarium's ecosystem.

      The first factor that affects an aquarium's pH is the water you use, which has an initial pH of its own. Adding fish and plants, both of which take what they need from the water and release waste back into it, can change the pH. So can leftover food as it breaks down. A dirty aquarium loses its ability to maintain a constant and life-sustaining pH. The pH balance can react adversely to even a brief change, such as putting your hand in the water.

    pH Management

    • Wood can be used as decoration and lower the pH of a fish tank.

      The pH of your tank should balance itself out naturally. You can buy kits to test the pH, but many aquarium hobbiests advise against treating pH chemically. Instead, look for long-term options to help your tank buffer itself against fluctuations. Adding aquarium-safe wood as a decoration or putting peat in the filtration system can lower pH, while a seashell or coral skeleton can raise it. It takes time, however. These additions will not bring about change overnight.

    Preferences of Various Fish

    • Unstable pH can kill a fish.

      Different fish species have different pH preferences, so it pays to research the types of fish you want to have. African cichlids like high pH levels, while discus prefer low levels. This alone means they don't make good tank mates. Most community fish, such as guppies, mollies, swordtails, zebra danios and platys, prefer a pH around neutral (7 to 8). Angelfish like a range from 5 to about 7.5, making them good tank mates for cardinal and neon tetras.