To maintain a healthy pond one needs aerated water to prevent the growth of anaerobic bacteria and the death of animal life. Aerated water is usually ensured through the use of a pump or fountain that improves both circulation and a water’s surface area, increasing the exchange of gases. Without such devices, aerated water can only be ensured through open water that is uncovered by plant life. Hence, the number of plants needed for a pond is dependent on whether you have a pump/fountain.
Pond plants are supplied in pots ranging from 9cm all the way to 30L. As a rule, we recommend no more than 9 9cm pots, 7 1L pots and 4 3L pots per sq m. Obviously, you can always repot your plants once they grow so a 9cm could eventually fill a larger pot. Further, some plants are more vigorous than others, hence we recommend only 1-2 lilies per sq m, less if you happen to buy a large pot or a vigorous variety.
It is worth noting that plants covering a pond’s surface can deprive a pond of oxygen, which is essential for both plants and fish. A still pond is only able to exchange gases at the water’s surface, where it absorbs oxygen and releases carbon dioxide and other gases.
You can improve the aeration of your pond through submersible pumps and fountains that act to increase the exchange of gas by increasing the surface area of the water and improving circulation. This is especially important in summer as the temperature of the water is inversely related to the amount of oxygen it can hold.
Oxygenating plants act to starve algae of both nutrients and carbon dioxide, reducing both algae blooms and anaerobic bacteria. Some nurseries recommend two per sq m. It should be noted, despite their name, their effect on aeration is minimal, as while they oxygenate in the day they withdraw oxygen at night. Hence, they are not a substitute for a good pump.
A lack of oxygen will lead to the growth of anaerobic bacteria, which produce gases such as hydrogen sulfide, leading to smelly ponds. It can also be dangerous for fish, who can be spotted gulping air. To remedy this purchase a more powerful pump, or remove fish and plants that both compete for oxygen.
Lastly, some pond plants, such as lilies, prefer still, calm water and are unsuitable for growing near pumps and fountains.
Jorge works in the Primrose marketing team. He is an avid reader, although struggles to stick to one topic!
His ideal afternoon would involve a long walk, before settling down for scones.
Jorge is a journeyman gardener with experience in growing crops.