What are the Effects of pH Changes in a Freshwater Aquarium?

Pondus hydrogenii, or pH, is the weight of hydrogen ions in water. The amount of acidity in water is expressed as the liquid's pH level. The pH scale runs from 1 to 14; a level of 7 is neutral. Below 7, the water is more acidic and above 7, the water is more alkaline. Most tropical fish do well in water with a pH level of 6.5 to 7.5.

  1. Causes of pH Change

    • Too much algae growth in your tank can raise its pH level.

      When your freshwater aquarium is not well-maintained or your under-gravel filter is clogged, the pH level may be thrown off balance. Carbonic acid is produced by excess waste in your tank. This acidifies the fishes' environment, lowering its pH. Setting up your aquarium in direct sunlight, or leaving the hood light on too long promotes excessive algae growth, and raises the pH in your aquarium.

    High Alkaline

    • Slight changes in the pH level of your aquarium water can be damaging to your fish. A pH level of 5.5 or below is a condition called acidosis. This high-alkaline or basic water can cause alkaline damage to your fish. Water that is too basic may affect your fishes' gills. It may also cause erratic behavior -- fish darting back and forth and jumping in the aquarium -- eventually resulting in death.

    High Acid

    • A fish's eyes can be damaged by pH level changes.

      Water that is too acidic promotes the development of toxic compounds. Acidic freshwater environments may cause your fish to produce excess mucous, gasping, eye damage or epithelial hyperplasia, which is a thickening of the skin or gills. If not corrected, aquarium water that is too acidic may cause your fish to die.

    Checking the pH Level

    • Monitor your freshwater aquarium's pH with a commercially available testing kit. Some use a dipstick coated with reactive dyes, which cause the stick to change color, indicating the water's pH level. Other kits come with reactive liquid that changes color when added to the water. The shelf life for pH testing kits is short. Check the kit's expiration date before using.

    Adjusting pH Levels

    • Peat is harvested as a fuel and can be used to lower an aquarium's pH level.

      Lower the pH in your freshwater aquarium by adding bogwood to your tank; filtering the water over peat; injecting carbon dioxide (CO2); or using a commercial buffering agent. In addition, you can amend the water with softened water or reverse osmosis/de-ionized (RO/DI). Raise the pH level of your freshwater tank by aerating it to reduce excess CO2; filtering the water over coral or limestone; adding limestone-rich rocks to your tank or a coral-sand substrate; or using a commercially available alkaline buffer.