Future Pets' Pond Manual
Testing & Buffering pH in Your Pond

Water pH is one of the most important parameters to consider when testing a pond. A pH that is too low or too high will affect the health of the fish and plants!

Ammonia toxicity depends on the pH of your water garden. More toxic ammonia is present in pH ranges above 7.0 than below.

Even if your pond has a low pH and low level of toxic ammonia before a water change, adding high pH water can instantly change the ammonia to a toxic form and damage fish and plants.

Each time you add or change water, it is a good idea to measure the ammonia level and treat accordingly or treat prophylactically every time with a product such as Ammonia Detox.

Since many water departments are now increasing pH it is necessary, in many cases, to lower pH to provide a safe environment for the fish and plants. How difficult it is to lower the pH a given amount is dependent on the alkalinity (or buffering capacity) of the tap water.

In some areas where alkalinity is low it is easy to lower the pH. In other areas, the alkalinity is extremely high, and excessive amounts of pH adjusting chemicals may be required.

Leaching of alkaline materials from concrete ponds may also contribute to the problem.

It is prudent to start off using a small amount of pH adjusting products at first. Adjust the pH multiple times, if necessary, to determine the amount required to lower the pH of your particular water to the proper value. Further experience will be required to determine when additions will be necessary to maintain the proper value.

"pH bounce" is the effect of treating your water, lowering the pH to the appropriate level and then, upon later testing, finding that the pH is again too high.

In highly alkaline waters (indicated by pH "bounce"), the alkalinity will be lowered with each addition of product, so that less will be required on each addition to cause the same pH drop.

If the pond is new, and concrete and alkaline rocks have been used, several changes of water will be necessary, and some aging (i.e. allowing some algae and sediment to cover the exposed alkaline materials to slow their leaching into the pond) will be required to get the pH under control.

Some tap water systems suffer a low pH (below 7.0). Pond pH may also degrade over time, becoming more and more acid. If pond pH is too low, fish and plants will suffer, although, plants may die in water that fish continue to live in due to low pH.

It is a good practice to measure pH weekly on new ponds and semi-monthly on established ones. Never change pH more than .2 pH per day! Maintain accurate records.

Courtesy of Kent Marine