How to Change pH With a Substrate

The measure of a substance's acidity, pH levels range from 0 to 14. Higher numbers are more alkaline, while lower numbers are more acidic. Pure water has a pH of 7. Most fish prefer pH ranging from 5.5 to 8.5, and it's important to maintain the pH of your aquarium's water at the level recommended for your particular species of fish. Substrate, the substance used to line the bottom of the aquarium, can raise or lower the pH of aquarium water, making it an excellent option for achieving the right levels for your fish.

Things You'll Need

  • pH testing kit
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Instructions

    • 1

      Research the appropriate pH level for your fish. Most pet stores provide brochures about particular species of fish and their pH needs. No one pH level is appropriate for all fish, so it's important to know your fish's particular needs before changing the pH.

    • 2

      Test the pH of your fish's water to determine if it needs to be raised or lowered. Testing kits are sold at pet and pond stores and come with detailed instructions. Insert the pH strip from the test kit into the water as directed and wait for it to change color. The color will correlate with a chart that comes with the testing kit. This chart will tell you the pH.

    • 3

      Raise the pH if it is too low. Crushed coral is the most effective choice for creating a more alkaline tank and will raise pH substantially. If you only need to raise pH a few tenths of a point, place crushed coral under aquarium gravel. Gravel that contains calcium and magnesium can also be used to raise pH. Some pet stores sell substrates designed to raise pH. These typically contain crushed coral and minerals. Read the instructions on the bag carefully to learn how high these substrates will raise your aquarium's pH and then choose accordingly.

    • 4

      Lower the pH if it is too high. Lowering aquarium pH is generally more difficult than raising it, and can result in an overabundance of ammonia if not done slowly. Peat moss will lower pH a small amount and is a good choice if the pH of your aquarium is only slightly high. Adding driftwood can also help to lower pH. Commercial substrates lower pH by adding carbon dioxide to the tank. Look for substrates that add this organic compound at your local pet store.