Most pond owners don’t have a stream feeding their pond in their yard. Therefore why go to the expense of adding movement? Why not just have a still pond that you can enjoy in the warmer months and let sleep when it’s frozen over in the winter?
A still pond is only able to exchange gases at the water surface. A still pond will support only a very small fish population. A pond not only needs to absorb oxygen from the air but it also needs to release other gases. Hydrogen sulfide is produced by anaerobic (without oxygen) bacteria breaking down organic matter in the bottom of the pond. The pond bottom has less oxygen than the upper layers of the pond. This is especially true if you have stone or gravel in the bottom of your pond. Anaerobic bacteria work in the absence of oxygen and cause a septic condition in the bottom of the pond.
You want to circulate water in the deep part of the pond to help with the breakdown of organic compounds. You will therefore have better water quality. During warm weather draw water up from the bottom of the pond to expose it to the atmosphere. When you expose water from the bottom of the pond to oxygen rich water you will have aerobic (uses oxygen) bacteria breaking down the organics. This will reduce foul odors in the pond, which are caused by anaerobic bacteria action. Therefore you want a moving pond for gas exchange and to reduce foul odors.
If your fish spend a lot of time at the surface sometimes gulping air then you most likely do not have enough circulation. By simply adding an air pump you can greatly increase the oxygen in the water. Therefore you want a moving pond to increase to oxygen in your pond and consequently improve the health of your pond life.
Another concern are mosquitoes. They breed in still water. If you have an air pump movement in the water can interfere with the female mosquito’s ability to lay eggs.
Movement in water will also maintain a hole in the ice in the winter when your pond can freeze over. Your fish and other pond life still need oxygen in the winter months so you need to maintain a hole in your ice. You also want undesirable gases still to escape from your pond so keeping a hole in your ice is essential. Therefore movement in your water created by an air pump will also ensure that your pond remains healthy through the winter months.
You can certainly have a still pond in your yard but it may not look, or smell, healthy so you may wish to consider adding an air pump. This will create enough movement in your pond to ensure that your pond remains healthy and attractive throughout the year.