How to Reduce the Alkalinity of Aquarium Water

Creating the perfect balances of chemicals in your aquarium contributes to the health of your pet fish. Within the community of your fish tank lies a complicated cycle affected by every action of your fish. The filter, decorations, plants and types of fish can make or break the chemical balance in your tank. High alkalinity results from the inability to obtain a constant pH over time. Alkalinity measures the ability of the chemicals in water to neutralize acid without changing the water's overall pH. This change is called buffering capacity. Reducing the alkalinity in of aquarium water will help prevent a fish die-off and stabilize your tank for healthy fish.

Things You'll Need

  • Aquarium water conditioner
  • pH test kit
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Instructions

    • 1

      Test the alkalinity of your tank using the pH test kit. Establish your baseline when your tank requires a water change. Test again after the filter has cycled the entire tank a few hours after a water change. In addition, also test your tap water to measure the alkalinity.

    • 2

      Understand that alkalinity is reflected in a high pH range measuring from 7.4 to 8.4. The ability of your tank to control alkalinity results from an established biological filtering system that creates a balance of chemical in your tank. Low alkalinity impedes this natural biological filtering system that consumes fish waste, excess food and algae.

    • 3

      Perform regular water changes on your tank. Unplug your filter and heater (15 minutes before to allow cooling) before changing the water. Remove one-third of your aquarium's water and replace with fresh, treated tap water. Replacing water improves the overall chemical complex of your tank faster and better than any other treatment method. Perform these water changes every other week. Clean filters and include fresh carbon filter cartridges at least once every other water change.

    • 4

      Do not overfeed your fish. Excess food settles on the bottom of the tank and upsets the balance of the nitrogen cycle. Feed only as much as your fish will eat in 1 to 2 minutes.

    • 5

      Monitor the healthy of your fish closely and limit the number of fish in your tank. As a general rule, populate your tank with 1 inch of fish per gallon of water. Overstocking and overfeeding are the main cause of fish kills and unstable tanks with high alkalinity.

    • 6

      Maintain a stable alkalinity level and pH for the type of fish in your tank. In general, pH ranges from 7.0 to 8.0 are ideal, although some species require much lower pHs. Make sure your fish can tolerate higher pHs. See additional resources for recommended pH levels for various types of fish.

    • 7

      Make any changes to the alkalinity level of your tank slowly. Fish require a very stable environment, so dropping the pH quickly will kill your fish. Lower pH by no more than 0.2 pH per 24-hour period to avoid sending your fish into shock.