Question
I have a koi pond in back yard, approx. 5000 gal. We used Aquascape mech. skimmer and biofalls and granite gravel. It's about 3 years old. I have always had a problem with ph over 8.2. The water stays cloudy and the plants are not doing well. I use both well water and city water to fill it. The ph of both water supplies is over 8. I have tried adding 10 gallons of white vinegar over a 5 day period several times but cannot keep the ph down.
Any suggestions??
thank you for your help.

Answer
Hello Gene. pH is a very problematic variable with pond owners including me. Vinegar can be used to lower pH, but, vinegar is basic. The pH of vinegar is between 8 and 9 on the pH scale.

Take care in using city water to fill your pond. Make sure you're using a chlorine/heavy metal neutralizer. Even well water has many metals that can be toxic to pond plants and fish too.

Here in St. Louis, tap water measures just above 9.0 on the pH scale. I use a granular fish safe acid called pH salts down. Whenever I top off my pond, I use some of that and a chlorine and heavy metal neutralizer. Now, to get your pH down below 8.2 should not be too difficult if your a product like pH salts down. Every application will lower the pH down .2 points on the scale. For example: if your pH is measuring 8.2, then 1 application will get you down to 8, another 7.8, then 7.6, so on and so forth. Ideally the pond should be around 7.0. This should help your water clarity and your plants too.

Thanks for writing Gene! Hope this helps.
Brigitte