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What if my pond has aeration and it still freezes over? Will my fish be okay? | Decorative Ponds & Water Gardens Q&A

What if my pond has aeration and it still freezes over? Will my fish be okay?

What if my pond has aeration and it still freezes over? Will my fish be okay?
Sue – Boston, MA

The reasons for aeration during the winter months are largely the same as they are during warmer weather. The oxygen provided by aeration is vital to the health of fish – all year ‘round. In the winter, aeration does double duty, both by introducing sufficient oxygen to the water, and by preventing the formation of ice that could contain harmful gases produced by leaves and other decaying material on the pond’s bottom. As long as the aerators keep some of the water from freezing, the fish in the pond will have sufficient oxygen to weather the cold.

If your aerator can’t keep up with the impact of a long cold snap, and the pond freezes entirely for a short time, your fish should be fine. Short term freezes shouldn’t pose a threat to a well maintained pond – and fish will have sufficient oxygen to survive the temporary freeze. During longer cold snaps, however, harmful gases can accumulate, and you may need to take measures to open the ice. To accomplish that task, it’s important to avoid the use of hammers, drills or other percussive tools. The effects of violent vibration can be harmful to fish. Instead, try applying buckets of hot water to melt vent holes.

To prevent freezing, we recommend the use of our Pond Logic® Water Garden Aeration Systems. With the system installed, it’s wise to prepare for winter by situating stones throughout the pond. For an added measure of assurance, you may also want to suspend some stones closer to the surface to generate more surface-level water movement, while leaving the bottom of the pond still for fish.

Pond Talk: Have you had your pond freeze over even with the help of an aerator?

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Can a Fountain Provide My Pond Sufficient Aeration? – Pond & Lake Q & A

Picture of a "V" Patterned Fountain.

Pond & Lake Q & A

Q: I would really like to have a fountain in my pond and I know I need aeration. Will a fountain aerate my pond? – Nathan of Florida

A: Having a fountain in your pond is a great way to add tranquility to your home. To sit out on the deck and see a beautiful fountain

display as well as hear that relaxing sound of water. What more could you ask for? Many people are drawn to a fountain’s show-stopping appeal, but will they aerate a pond as well? The answer to this really depends on a couple factors: the pond’s depth and the type of fountain pattern the fountain is using.

Pond’s Depth: Fountains can be great aerators when the pond is less than 6′ of depth. The reason for this is because the best way to aerate is to circulate the whole body of water at the same time. A fountain will only draw water from the top of the water column, which is water that already contains oxygen from the air to water oxygen transfer. The pond’s bottom will remain untouched if it is deeper than 6′. If your pond is less than 6′ deep, then all you have to worry about is the spray pattern.

Fountain Spray Pattern: The spray pattern of a fountain makes a huge difference in how much aeration is produced. Usually the more decorative the spray pattern, the less likely it is to aerate your pond properly. This is because more energy is spent on creating the decorative pattern than there is moving the water. The best spray pattern to use for a fountain is a “V” patterned fountain like the picture above

If your pond is deeper than 6′ of depth, than the best method of aeration would be an Airmax Aeration System. The Airmax Aeration System diffuser will pump air down to the bottom of the pond, and the resulting column of rising bubbles lifts and aerates the water. By starting from the bottom, up, this will ensure that the whole body of water is properly circulated as well as aerated.

Why Did My Fish Die Over the Winter? – Pond & Lake Q & A

Illustration of No Aeration Versus with Airmax Aeration

Pond & Lake Q & A

Q: I lost all of my fish after the winter. We love to catch fish in the pond and now we have to start over! What happened? And is there anything I can do to prevent this from happening again? – Alfred of Michigan

A: My first thought when I read this question was, “They don’t have an aeration system”. And after speaking with him, come to find out, he didn’t. This is usually always the case during a winter fish kill. Everything seems to be going just fine when all of a sudden one morning you wake up to discover a wave of fish floating on your pond’s surface. This is not a pretty sight, nor is it any fun to clean up. So what causes fish kill and what can you do to prevent it?

What Causes Fish Kill?
During the warmer months of the year a pond with no aeration will contain oxygen towards the surface of the pond. This is because there is an oxygen transfer from air to water at the pond’s surface. The bottom of the pond, however, will contain very little or no oxygen; Certainly not enough to support fish life. Also, the toxins associated with fish waste and other organic biodegradation tend to sink and stay at those lower depths of the pond, polluting the already oxygen-starved water. This unfortunately, condenses your fishes’ habitat area and forces them to live towards the surface of the pond.

There is also a difference in temperature from the bottom of the pond to the surface. The bottom of the pond will be colder than the pond’s surface. The reason for this is because the sun will heat up the surface of the water and since cold water is denser than warmer water, the cold water will fall to the bottom. This difference in temperatures can be quite dramatic at times. Have you ever jumped into a pond and felt the brisk cold water towards your feet? This is the thermocline border. This dramatic change in temperature can cause your fish to stress as they travel from a warm temperature to a cold temperature and back to warm. This stress can lower their immune systems.

During the colder months of the year, the oxygen as well as the thermocline will actually flip. All of a sudden the colder water containing no oxygen will mix with the warmer water with oxygen. As this mixing occurs, the fish are left with few places to go for oxygen and they will eventually suffocate.

Another issue during the winter are toxic gasses. As bottom organics (grass clippings, leaves, trees, twigs, fish waste, etc.) decay, they will create toxic gasses. When ice covers the pond’s surface, these toxic gasses are trapped underneath the ice and will cause a fish kill.

Preventing Fish Kills
Using an Airmax Aeration System is the single most important way to help prevent winter fish kills. The reasons are simple: With an Airmax Aeration System, a compressor sits on shore and pumps air down to a diffuser on the pond’s bottom. This air forces the cold water containing no oxygen to the pond’s surface. This water, because it is denser, will fall back to the pond’s bottom. This cycle will repeat and create a convection or current within the water column. This will fill the whole water body with oxygen as well as maintain the same temperature level throughout the pond (see illustration on left).

Also, during the winter months, when ice has covered the surface of the pond. An Airmax Aeration System will keep a small hole open in the ice to allow those toxic gases to escape.

The Bottom Line: Having aeration will help reduce the chances of fish kill. Also, remember that this is one of many benefits of having an aeration system (Refer to this blog post for the other benefits of aeration).

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