Keeping your pond properly aerated is a key part of making sure it stays healthy particularly if it is stocked with fish. Although a certain amount of oxygen diffuses naturally into the water at its surface, most ponds will need some additional help, unless they are fairly large or contain only a very small number of fish.
A good choice of plants can be one of the simplest ways to improve the amount of dissolved oxygen in the pond. Most aquatic plants are easy to look after, growing well and making few demands beyond an occasional spot of tidying-up. However, it is important to select carefully, bearing the size and depth of the pond in mind, since some of the kinds sold can be a bit too vigorous for the smaller water garden. Canadian pond weed (Elodea canadensis) is one of these – really only suitable for larger ponds, unless you are prepared for a good deal of thinning out. Other types of Elodea – such as E. crispa or E. densa – are better bets for small water features and just as effective oxygenators. The native curled pondweed (Potamogeton crispus) makes a good alternative, particularly for ponds intended as wildlife habitats. As well as improving aeration, oxygenating plants also help pond health by absorbing excess nutrients which can otherwise fuel algal blooms.
Making a Splash
Moving water has always been a part of pond-keeping and a fountain or waterfall feature plays an important role in helping with aeration – as well as adding a dynamic dimension to the whole feature. A good splash helps enhance the natural diffusion of oxygen at the surface and the underwater currents it sets up aids the spread of aerated water around the pond. There are plenty of options available so there should be something to suit all tastes and types of water-garden.
Most modern pumps come with spray attachments allowing a simple fountain to be added quickly and easily, while if you prefer something more substantial, there are any number of fountain ornaments available to provide the perfect centre-piece for any pond. Making a cascade feature takes a bit more effort, but a properly constructed waterfall is hard to beat and is certainly a highly effective way of adding oxygen.
Whether you choose to have a fountain or a waterfall, it is generally easier to plan to install it when you build the pond if you possibly can, as fitting it afterwards can be a bit of a fiddle. It is also worthwhile giving some thought to the power supply at the outset, not least from the point of view of safety – so professional advice from a qualified electrician is always a good idea. Making the most of the aeration effects depends on getting the flow-rate and surface splashing right, so when purchasing a pump for a water feature, it is important to pay attention to its capacity – how high it will pump and the volume it can handle in an hour. Both of these figures can usually be found on the box, so making your selection becomes quite straightforward. For a waterfall, the flow rate required can be worked out by allowing at least 150 litres per hour for every one centimetre of the waterfall’s width, while for a fountain, the greater the height, the more impressive the spray and the more disturbance at the surface to trap air.
In today’s eco-aware world, it is little surprise that environmentally-friendly products are available to help the “green” pond-keeper. While most waterfalls and fountains are still driven by traditional pumps using mains electricity, the latest generation of solar powered versions are becoming increasingly popular. Quite apart from their obvious low-carbon appeal and low running costs, they remove the need for a convenient power source, waterproof junctions, residual current devices (RCDs) and cable protection, making installation a much simpler undertaking.
Solar-powered aerators are also available which work like the air pumps in fish-tanks – attaching to a perforated artificial stone and bubbling air directly into the water. Although many of them are designed for quite small ponds, they can also be used very effectively to supplement other methods of aeration in larger ponds too.
Solar-powered equipment, inevitably, works at its best during the sunnier months, which fortunately coincides with the pond’s maximum need for additional oxygen. Since warm water naturally holds less oxygen than cold and fish and other aquatic life are at their most active in the summer, the “green” solution can certainly play its part.
Aerating your pond brings major benefits to the aquatic life and water quality but whichever method you chose, it also improves things in other ways too. Carefully selected oxygenating plants, used imaginatively, can help bring the pond alive and provide a focal point throughout most of the year, while the sight and sound of running water adds an entirely new dimension to any garden. It is the best of “win-win” situations.