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How to Lower the PH in a Fish Pond

| Updated September 26, 2017

Things You'll Need

  • pH Test Strip

  • White vinegar

Maintaining a proper and stable pH level in your fish pond is a key to having healthy fish that will live until maturity. Having a pH level too low becomes too acidic and harms your fish, as well having a pH level too high causes toxicity in your fishes' living environment. A proper pH level for a healthy fish pond is between 6 and 8.5 pH. Any level higher than 8.5 will stress the fish and cause disease.

Measure your pond's pH level using a pH test strip that you place in the water for two to three seconds and wait for the results to appear on the strip. If your pH levels are not in the 6-to-8.5 pH Safe Zone, you will have to conduct a water change-out.

Change out your water supply according to your pH level readout. If your pH level was around the 9 reading, you will need to conduct a 10-to-25 percent daily water change-out. If you had a reading in the 10 pH range, you will need to conduct a 25-to-50 percent water change-out. If you have a reading above 10 pH, you must move all fish into a hospital tank and change all the water in the pond. A hospital tank is composed of pH balanced water suitable for your fish type, proper lighting, tank stones, a heater and an air pump. The fish must be there for a minimum of 24 hours to see no signs of disease.

After the first change-out, monitor your pH levels daily, and if the pH level does not lower into the suitable 6-to-8.5 pH range, add one cup of white vinegar for every 1,000 gallons in your fish pond. For example, if your fish pond is 250 gallons, use only a quarter of a cup of white vinegar.


  • Always have a hospital tank available for your fish for pH emergencies.