Testing & Understanding pH Buffers 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 and pH

Ammonia toxicity depends on the pH of your water garden. Ammonia comes from the waste of fish, fish food, decay and debris. It can becomes toxic when combined with high pH water. More toxic ammonia is present in pH ranges above 7.0 than below.

Where Does Alkalinity (high pH) Come From?

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 any ammonia in your pond to a toxic form and damage or kill fish and plants.

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.

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

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

How Much pH Buffer Do I need?

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.

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.

What is pH Bounce?

"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.

What About LOW pH?

Some tap water systems suffer a LOW pH (below 7.0). Established ponds may also degrade pH 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