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Aerating Your Pond

By: Dr Gareth Evans - Updated: 22 Jul 2018 | comments*Discuss
Aeration Pond Health Fish Oxygen

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.

Going Green

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.

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We have rattailed larvae in our washing up pond along with some midge larvae. As our cats keep drinking the water should we remove them and what can we do to improve the health of the pond. We have 3 small oxygenating (at least we thought they were) plants in the pond - they look like tufts of grass. Do we need to have an aerator to help improve the condition? Thank you
Edward - 22-Jul-18 @ 2:15 PM
I want to use "Paddle Wheel Aerator" in my small pond. May I put my queries?
talora - 25-Aug-17 @ 4:32 PM
frogs will mate anything that moves so unfortunatly frogs think fish are good mating material hence the demise of your poor fish
kat - 5-Jul-14 @ 8:04 PM
I have a small raised patio pond. There were four small (4-5 inches) Koi Carp living happily in the pond forfo the last year. The pond has good aeration provided by a filter pump / fountain and an electrical artificial stone aerator. Approximately half the pond around the edges have marginal plants (stood on bricks -plenty of hiding places for the fish). Four weeks ago I found a fish dead at the bottom of the pond, on inspection I found a frog grasping the fish tightly and a chunk of the fishes flesh had been taken from its back. The frog was released at the back of my garden and the fish put in the green wheels bin. Yesterday I found a a dead fish floating on the surface of the pond again with chunk of flesh missing from its back. I netted the pond but found no frogs. A frog was seen at the side of the pond - removed to the back of garden. Please can you help me with a solution to this problem. Thank you.
bazzer - 2-Jul-14 @ 11:09 AM
Hi, I have a small pond in which I have successfully kept 7 goldfish. 2 years ago a number of fry appeared. Ultimately we had about 20 growing fry, and managed to net 6 to give to other fish-keepers. But, now have only 4 adult fish, (3 disappeared in early Spring this year; and around 12-15 small fish. Efforts to catch them have recently 'failed' as they seem to have got wiser! We have a fountain, filter and pump, and de-leaf from the surface, but I know we have silt. Can you please advise on how best to de-silt? I would prefer organic solution if possible as catching the fish is so stressful for them, some of the young fish are charcoal and difficult to see and catch,as we discovered last year..... I would say that the pond is otherwise in a good condition. Each Spring, I use a general water conditioner. I would appreciate your expertise.
Suzie - 13-Jun-14 @ 9:54 AM
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