How to Fix a High pH Balance in a Saltwater Aquarium

Written by jessica kolifrath
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How to Fix a High pH Balance in a Saltwater Aquarium
Keeping your saltwater aquarium healthy includes regulating the pH balance. (aquarium fish 7 image by cherie from

Although the healthy pH level for a saltwater aquarium is naturally higher than for a freshwater aquarium, it's still possible for the pH levels to rise too high. High pH levels reflect alkaline water, and if the alkalinity of the water is too high, the sensitive reefs and fish in the aquarium could be damaged. With regular testing and adjustments, any saltwater aquarium can be kept at a healthy pH level. If you have recently tested your aquarium and found the pH levels to be too high, lowering the pH balance in a saltwater aquarium is a simple task.

Skill level:

Things you need

  • Aquarium pH testing kit
  • Aquarium siphoning tube
  • Bucket
  • Vinegar or lemon juice
  • pH reduction chemical
  • pH buffer additive

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  1. 1

    Test the aquarium's pH balance. Testing should be performed every two weeks, as well as after any important change in the tank, such as a fish dying or becoming ill.

  2. 2

    Know the optimal pH balance levels for all of the fish, coral and plants in the aquarium. Most saltwater aquarium life prefers a pH level over 8.0, but some fish have more specific requirements.

  3. 3

    Adjust high pH levels slowly, over the course of a week or more. If your testing kit registers a dangerously high level, such as a score of 10 or more, add a single drop of lemon juice or plain white vinegar to the tank to begin lowering it immediately. According to Thomas Sasala at the Fish Information Network, these household staples can safely lower a high pH without damaging the tank.

  4. 4

    Use a specially designed pH reduction chemical, commonly found at pet stores and aquarium supply stores, to carefully lower the tank's pH level. Test a few hours after each addition of the chemical. The experts at the Advanced Aquarist's website warn against lowering the tank's pH level more than half a level for every three days, as this can shock the fish and plants in the tank.

  5. 5

    Add a specially designed saltwater pH buffer mix to avoid unusually high or low pH levels in the tank. These contain the calcium, iodine and other important chemicals present in seawater that keep the pH level from dropping or raising unexpectedly.

  6. 6

    Avoid unwanted fluctuations in the tank's pH balance by performing regular partial water changes. Use an aquarium siphon to remove one-eighth of the aquarium's water, then replace it with bottled water.

Tips and warnings

  • Check the salt mix of the aquarium's water regularly as well, especially after a water change.
  • If the tank contains delicate live coral that require a precise alkalinity and high amounts of calcium, consider installing a calcium reactor.
  • Know the pH balance preferences of any fish, coral or plant you want to add to your aquarium, and reconsider your decision if the tank's current pH balance will not fit it's needs.
  • Do not attempt to drastically lower the pH balance of the aquarium. The change can shock the fish and plants, and will kill delicate specimens.
  • Do not add more than a single drop of lemon juice or vinegar to the tank, and do not use it in place of a specially formulated pH reduction chemical.
  • Do not change more than one-fourth of a saltwater tank's water at a time, or the salt mix may become unbalanced and damage the tank's health.

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