Knowing the water volume in a fish pond is useful information for several reasons, such as calculating the amount of algicide, water clarifier or other chemicals to use safely in the pond. Virtually all pond additives are based on a ratio of water volume to the chemical, so total volume in the pond becomes important to the health of aquatic life when treating the water. Since most ponds have irregular shapes, making linear measurements difficult, calculate volume based on the rate of water flow when filling the pond.
Connect a garden hose to a water faucet, turning the hose coupler counter-clockwise, and insert the other end into a 5-gallon container.
Open the water faucet valve quickly and as far as it will go, starting the stop watch or other device at the same time.
Stop the watch or timer when the container fills with water and note the elapsed time, for example, five minutes. The water from the faucet flows at a rate of 1 gallon per minute.
Insert the hose into the empty pond, turn on the water and start the timer. Stop the timer when the pond is full.
Calculate the volume in the pond by dividing the number of minutes it takes to fill the pond by one, which is the rate of water flow in gallons per minute. For example, if the pond takes three and a half hours to fill, that equals 210 gallons (3 1/2 hours equals 210 minutes).