Dan Everton explains that keeping a pond healthy requires a combination of nature and technology right from the planning stage.
At the planning stage there are simple rules to follow when placing a pond in your garden. Position it away from trees to lessen the chances of leaves falling into the water, but shaded from direct sunlight for a good portion of the day. Make sure the water is at least 2ft deep, ideally 3ft if you are keeping fish, with marginal shelves for plants.
Maintaining Good Water Quality
Once in place you need to ensure that water quality is maintained to encourage a flourishing environment for plants and wildlife. The water should flow and oxygenate rather than stagnate. The ideal way of achieving this is to introduce a feature such as a fountain or waterfall.
To calculate the size of the pond pump you require to feed the feature remember that water should be circulated at least once every two hours i.e. a 300 gallon pond will need a pump that generates a flow of 150 gallons per hour.
Next consider what you are asking the pump to do and bear in mind that it always pays to buy a pump with a capacity above what you need, as you may want to add features at a late date.
To be absolutely sure that you get the right pump for the job, arm yourself with these facts, refer to manufacturer’s specifications or ask advice at your garden centre:
- The volume of water in the pond
- Total head height of any fountains and waterfall the width of any waterfall, the total length of hosing used
- Filtration is also essential to prevent the build-up of nutrients and impurities and ensure clean, healthy water.
- Mechanical filters trap dirt and debris, effectively cleaning the water of elements that may feed algae or are otherwise harmful to pond life.
- Biological filters provide a medium in which beneﬁcial bacteria can multiply and break down harmful toxins such as ammonia resulting from ﬁsh waste..
- Chemical ﬁltration is also effective against non-filterable pollutants and refers to the process of controlling and changing speciﬁc water conditions so that, for example, phosphate and nitrates are trapped and eliminated.
- Finally UV clarifiers kill algae before it spreads and are particularly effective against ‘green water’
As these processes can be combined, for example filter kits may contain mechanical and biological filters together with a UV clarifier and they come in a range of formats such as pressure filters, gravity fed filters, pre-filters, specialist koi filters – it is no surprise that the choice is daunting.
Standard box filters are available for ponds containing 1000 – 10,000 litres, they can be mechanical and biological, with or without a UV clarifier fitted. Pressurised units allow you the option of powering a waterfall or fountain and more expensive filters feature advanced technology and can handle larger volumes of water.
When choosing a filter, consider what is most appropriate for your particular requirements. Follow the manufacturer’s recommendations on the filter’s capacity and the volume of water it can process. Don’t forget that if you have fish, take into account how many and how large they are, as this can dramatically affect the specification that is required.
Planting Is Important
Aim to have a good variety of plants. These are not only decorative but help to keep the pond in good shape.
Algae depend on sunlight, carbon dioxide and dissolved minerals for survival, so use water lilies and similar floating plants to cover about half the surface, shading the pond from sunshine. Submerged oxygenating plants will also reduce algae by absorbing minerals and carbon dioxide from the water.
If algae does invade the pond remove as much as you can with a stick or net and then treat with a wildlife friendly treatment such as Barley Straw extract that will kill the algae or one that removes the nutrients that the algae feeds on. Once eliminated, your water pump and filtration system should prevent any re-occurrence.
Prevent foliage from falling into the water (netting is useful in the autumn) and remove any rotting organic matter such as dead leaves from the pond as the gases released by decaying foliage are harmful to plant and wild life especially if they become trapped by winter ice.
Too Many Fish
The nitrate content of your water will increase if you keep fish, so don’t overstock. A rule of thumb is one inch of fish per sq ft of surface area (or 25cm per sq metre). Remember it’s always better to have fewer than too many fish especially in the summer when there is less oxygen in the water.
In case this or something similar is happening, it is always wise to test the pH of the water at regular intervals. Test kits are cheap to buy and easy to use to discover if the water is unbalanced. If remedial action needs to be taken, there are a range of treatments available to rectify any problem.