How to Change the pH in Fish Tanks

An aquarium's pH measures the acidity or alkalinity of its water. Many aquarium owners worry about achieving a certain pH level in their tanks. Luckily, while the ideal pH varies between different types of fish, the majority of fish are very adaptive and able to survive in a fairly wide range of pH. In fact, even exotic fish, which tend to prefer more specific pH, are really only so particular about pH when they are breeding. Instead, aquarium owners should focus on maintaining a constant pH.

In cases where the pH is too extreme, it is helpful to know how to adjust the pH of an aquarium's water and keep the pH at a constant level.

Instructions

    • 1

      Decide whether it is necessary to adjust the pH of your aquarium's water. Fish are usually able to adapt to conditions that are slightly lower or higher than their ideal pH. Playing with the pH of a fish tank can be risky: a sudden change or vacillating conditions can be fatal to the fish. Ask yourself about the current pH, the ideal pH and whether the pH seems to be affecting your fish. If you have noticed any problems with your fish, make sure that their feeding and diet, the salinity, filter or temperature could not be causing it before attempting to change the pH.

    • 2

      Raising the pH of water tends to be easier than lowering it. Over time, pH tends to decrease, so replacing the water from time to time can help raise the pH. Pet stores often sell products that can help increase pH. To avoid shocking the fish, changing a small amount of water in 24-hour shifts prevents a drastic pH change. Some aquarium decorations contain buffering salts, such as limestone rock, shells or petrified coral, which can increase pH when placed in an aquarium. Aerating the tank, or increasing the concentration of oxygen in the water, will decrease the level of carbon dioxide and help to increase the pH. Most pet shops also have a variety of commercial buffers or "pH-up" solutions that, when added to the tank water, will increase pH. It is best to use such chemicals as a last resort since their use can lead to drastic changes in pH.

    • 3

      Attempting to lower the pH can prove to be more difficult, especially in hard water (low KH) as it has a high-buffering capacity and is more resistant to pH change. Filtering water through peat moss is one of the most effective ways to decrease pH and is especially effective in hard water. Adding wood to the aquarium can lower pH, as can adding carbon dioxide. Pet shops also feature some chemical products that can lower pH. However, these products do not cause a consistent, stable pH and can be dangerous to your fish.