Keeping your pond healthy is the goal of most pond owners and maintaining ideal seasonal temperatures is the key to thriving water gardens. For most aquatic life, but specifically fish, sustaining specific temperatures each season will depend on their survival. So it’s important to have a close eye on how warm or cold the water is. Water temperature takes a long time to heat or cool compared to the air so having a thermometer is vital to determine proper temperature for the health and safety of your pond.
How deep or shallow your pond is will also determine water temperature. Light decreases exponentially with depth in the water column so the sun can heat a greater proportion of the water in a shallow pond rather than in a deep pond. This means the shallow pond can warm up faster and to a higher temperature. This is why the air temperature may be cold but the lower layers of water remain warmer. This serves an important function for the survival of aquatic life during different seasons. During the winter, warmer layers at the bottom of the pond allow fish and plants to survive the cold weather. Checking the water temperature often with the thermometer allows you to make sure the colder water at the top is not hyper-cooling the warmer waters at the bottom. The temperature also determines when you should feed your fish. Check out our guidelines on when, what, and how much to feed your fish through out the seasons.
Now that we know how the pond water heats and cools, below is a guide determining ideal water temperatures for each season:
Across the US, water temperatures start to dip in September and October. Around this time, the water should be at about 70°F and as the temperature cools off through out autumn, it’s ideal for it to drop to about 55°F by December. Maintaining this temperature will allow the aquatic life to adjust properly to changing seasons and prepare for the upcoming cold months.
Trying to maintain a 40°F temperature is advised for the health of your aquatic life. Once the temperature drops below 40°F, turn off any running water such as fountains or waterfalls as well as pumps. Make sure that your pond is deep enough. As the temperature decreases, your fish will retreat to the deeper areas of the pond, where the water is warmer. If you live in an area where your water freezes, keep part of your pond open so that the toxic gases can be released. A deicer works well to allow the exchange of gases.
As the temperature begins to increase, your pond will start to warm up and the desired temperature should be from 55-65°F. This is a dangerous time for fish as they are coming out of a dormant state as well as bacteria from the rest of the pond. The fish’s immune systems are weak until about 65°F where they are stronger and more active and able to survive the bacteria.
The perfect summer pond water should be in the range of 68-74°F. Water loses much of its ability to hold dissolved oxygen when the temperature is above 85°F. Your fish are more active and competing with the rest of the aquatic life for a small amount of oxygen during this time, which can lead to fish kill. This is when aerators, fountains, and waterfalls help oxygenate the water. The other benefit of these aeration devices is that they also decrease the growth of algae!
Follow these guidelines to keep your pond healthy and strong to enjoy all year round!