Fish breeding in open pond. What is important in winter? Aeration.
The key to successful over-wintering of fish is pond aeration in winter. Fish need to breath and feed in winter as well as summer. However, during winter the water temperature is low so the metabolism and growing is much slower, but fish do not require intensive feeding – it is actually harmful. In winter they use the nutrients eaten in autumn and “snack” on the feed available in water – on plants or the ground – and the fish will be satisfied if they are given additional feed only once a week. However stopping the suffocating of fish is critically important for successful over-wintering of fish, so you have to pay attention to pond aeration. There are several factors that influence the life quality of fish in ponds:
- water temperature;
- the amount of nitrogen in water;
- the amount if nitrogen compounds in water.
In winter the water temperature in pond varies from 0℃ on the top by the ice to +4℃ and +6℃ at the bottom of the pond. Fish choose the warmest water, so they stay on the bottom. At the same time, bottom is where nitrogen compounds harmful for fish are concentrated, so the water there is filled with toxic gasses and can cause the suffocation of the fish.
The oxygen needed for breathing is supplied by water plants during photosynthesis or with direct contact between water and air.
The pond needs to be aerated to have sufficient amount of oxygen in the water and to prevent the profusion of carbon dioxide. Aeration means releasing the nitrogen compounds from the water and sufficient insertion of oxygen in the water. That is pond aeration and can be achieved using several methods.
Water plants will emit oxygen, if they are in light. Light will reach them if the ice covering the water is clean from snow. Also, cleaning the snow will not only cause photosynthesis in plants, but also improve the well-being of fish as they will realize the circadian rhythm.
You can get rid of the toxic gases by creating direct contact between water and air – the gases will leave the water, mix with atmosphere and they will be carried away by the wind. Ice-holes will be helpful for that. However, do not create the ice-hole using a hammer of hitting the water in any other way, as it upsets and stuns the fish. Drilling and sawing (don’t use a motor-saw as the oil from the saw will get in the water) are much better methods for making the ice-holes.
pond aeration in winter
You must also remember that the total area of ice holes should be as large as possible. And several small ice-holes will not achieve the optional area and only the top layers of water touch air. You must also remember that the toxic nitrogen gases are concentrated in the warmest water at the bottom of the pond, and those are the layers of water that need the airing the most. A simple solution is lowering a pump in the water. It will pump the water to the top of ice and let it flow back in the pond through another ice-hole. This way large volume of water will be aerated, however you must be careful because the lowest layers of water hold the heat and if you pump it upwards, the water and the pond will cool down too much. It would be wiser to insert the pump in the middle of pond depthwise. In this case the water at the bottom will not mix and cool down, but will release the excess nitrogen gradually in contact with the colder water. Now the pond will have higher temperature and fish will feel better.
pond aeration in winter
Another option is pumping air into water. If you insert airline tubes to the bottom of the pond and insert air bubbles through them. The bubbles will mix the water and help excrete the excess nitrogen. The bubbles may also hold back freezing of the water. You must also remember that larger bubbles have smaller surface than large number of small bubbles. Small bubbles can be delivered with specially made ceramic diffusers with microscopic diameter of holes or with diffuser pipes. These devices create so small bubbles that they are invisible with eye and water simply looks lighter. The surface of those bubbles is thousands of times larger and will rid the water of excess nitrogen. Fish will love it. However, the waves created by the bubbles will not be large enough to stop the pond from freezing. That can be achieved with another device – aerator. If you want to angle in your pond during winter, you’ll need floating or submerged water aerator. This device – a pump – projects a very emulsified spray of water into the air and then releases the water back into the pond using pressure. This movement of water will mix the top layers of water and create waves of water that will stop pond’s surface of freezing.
We suggest our clients to use the trustworthy aerators made by Faivre. Faivre is a French company – one of the leading manufacturers of aquaculture products in the world.