How to Lower the pH in a Marine Aquarium

It is rare that you would need to lower the pH in a marine aquarium. Generally speaking, tap water is between a pH of 6.0 and 8.5. Only at the upper end of this scale would the home aquarist need to lower the pH of the fish tank because calcium is falling out of solution. The pH of seawater is generally between 8.0 and 8.3, which is the range you should aim for in the aquarium as well.

Things You'll Need

  • Marine salt
  • Water
  • Non-calcareous gravel
  • pH tester
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Instructions

    • 1

      Test the pH of the water in your aquarium and the source water.

    • 2

      Make 10 to 20 percent water changes on a weekly basis if your source water is lower in pH than your aquarium water. If your source water is higher than your desired pH, then find a new water source. Deionized water can be obtained fairly cheaply, or reverse osmosis water can be used.

    • 3

      Remove shells and coral decorations. This is not practical if you have a reef tank.

    • 4

      Replace some of your dolomite or crushed coral aquarium substrate with aquarium gravel. Make sure the gravel is approved for saltwater aquariums.