Pond test kits are important accessories for maintaining a healthy, vibrant pond. They are inexpensive, very easy to use, and alert owners to potentially harmful conditions as they develop in a pond. Water gardens rarely need adjustment, although phosphate and nitrate levels are important factors in determining whether or not pond lilies and lotuses produce blossoms. Water quality in a fish pond, however, is a critical factor.
Fish produce waste products that contain ammonia, which is sometimes abbreviated as NH3. Ammonia is toxic to fish. In a restricted environment like a pond, NH3 can quickly rise to toxic levels and kill Koi or native species. Biological filters house colonies of bacteria that feed on NH3 as water circulates through the filter, but the activity of the bacteria fluctuates with temperature, and NH3 levels can sometimes spike. A pond test kit allows owners to detect NH3 in pond water and take preventative measures to protect fish.
In the first step of the pond nitrogen cycle, the bacteria in the biological filter convert NH3 to nitrite. Nitrite, which is often abbreviated as NO2-, is less toxic than NH3, but it is also toxic to fish. In a healthy pond, a second kind of bacteria converts the NO2- to nitrate, or NO3. Nitrate is harmless to fish and is used as a nutrient by aquatic plants. The nitrogen cycle is a natural process, and it is not common for NH3 or NO2- to get out of control in established ponds. It can happen, however, and periodic testing of the water will give pond owners an early warning of nitrogen waste problems while there is still time to take corrective actions.
Pond water test kits also measure the pH of the water. Seven is a neutral value. Values higher than seven indicate water that is alkaline; values below seven indicate acidic water. When new water is added to a pond, the pH can change. Rain water or well water is sometimes slightly acidic. Chemicals leaching into the pond from rocks or soil can cause the level to become slightly alkaline. It is an easy parameter to adjust, but only test measurements can determine whether or not adjustments are needed.
The most common pond test kits contain thin plastic strips with a test pad for each parameter. When the strips are dipped into the pond water, chemicals in the pads cause them to change color over time. At the end of a specified time period, the colors of the pads are compared to a reference chart. The result of the test is indicated by the color of the corresponding pad.
Another commonly available kit and the most accurate kit contain liquids that are added to vials of pond water. The chemicals in the liquids cause the water to change colors, like the pads on the test strips. A comparison of the final color of the water with a reference chart or color wheel indicates the test result.