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Build Your Own Garden Pond


pond


Make this the year you create the garden pond you’ve always wanted but have somehow never got round to. Something low maintenance yet beautiful, a tranquil place to sit by on weekends with friends and a glass of wine, or somewhere to attract wildlife visitors to your garden. Garden ponds are a haven for them, providing a habitat for frogs, newts, invertebrates, and fish, as well as offering a valuable supply of water for birds, hedgehogs, foxes, and other creatures. By considering wildlife in your design, you can create a pond that will bring your garden to life with both animals and plants.


frog      dragonfly

Before you start

It's easy to create a simple pond in your own garden but:

  • Consider the view of the pond from every angle of the garden and house. In a formal garden a square, rectangular or circular pond looks best and in less formal gardens an irregular shape looks more natural. Mark out the pond area with a hosepipe or length of rope, trying out different shapes and sizes. Once you've decided on a design, it's a good idea to view it from an upstairs window to see how it fits into the rest of the garden
  • Make sure there are no power lines or pipes located in the area where you'll be working.
  • Will you use a liner or a preformed pool?
  • Consider size as it will affect the suitability of the pond for its intended purpose, as well as its overall cost. As with style, the size of the pond should reflect the garden – a large pond in a small space will look out of place. When allocating space, remember that you will need an area around the pond for external equipment, edging (e.g. plants or slabs), and to allow sufficient access
  • Look into safety – ponds are not advisable in gardens if you have young children or children that visit unless you take steps to reduce the chance of accidents such as securing steel mesh frames over the pond that can take the weight of young children
  • Consult your local garden centre or supplier of garden pond products as they will be able to offer free advice on all aspects of construction, planting and maintenance.·        
  • Consider the type of plants you wish to grow. Different plants require different depths of water. 

Position

  • Ideally, the pond should receive 6 hours of sunlight a day to aid plant growth without encouraging excessive algae.
  • Electricity – pond equipment like pumps requires it so ensure the pond is somewhere a supply can be installed by a qualified installer.
  • As mentioned above the pond should be accessible for occasional maintenance plus planting, adding fish etc.
  • Trees – roots from trees can damage lining materials, so avoid placing your pond near them plus falling leaves can be a nuisance but these can be kept out with a net if necessary.
  • Drainage – don’t place your pond in an area that gets waterlogged, as it will disrupt the liner and potentially cause permanent damage. A well-drained area is best, or alternatively, you may need to install some additional drainage

Creating Your Pond

  • There are a number of ways of creating a pond. Most involve excavating a hole of the required shape: what is different is the type of impervious material used to line the hole. These include flexible waterproof liners, semi-solid preformed ponds and concrete.
  • Where fish and water plants need to be accommodated try to aim for a minimum surface area of 38 sq ft (3.5 sqm) to ensure the water is kept well aerated and clear. Smaller ponds will require an artificial filtration system.
  • The depth of water depends on the kind of plants and should be not less than 75cm (30in) to allow maximum planting range.
  • Water less than 15in (38cm) deep is liable to overheat in summer causing deoxygenation for fish, algal blooms and freezing in winter. A small but deeper pool is often most practicable but with at least one shallowly sloping edge for wildlife.
  • All ponds should have slightly sloping sides at about 20 degrees to make them less vulnerable to winter ice pressure.

Types of pools

Butyl: flexible

Flexible liners allow maximum freedom of shape and size and are particularly suited to creating a natural look. Butyl is a rubber material, heavier and more expensive than PVC but easy to install and with a life of 25-50 years or more plus it can be successfully patched if accidentally pierced.

Preformed: rigid

Cast in various shapes and sizes from reinforced plastic or fibreglass these are rigid and lightweight. Often they include planting ledges for marginal plants. They are relatively easy to install with a  range of shapes and sizes. They are best suited to small features. 

Concrete: rigid

Is the most durable of pool lining materials when soundly constructed and particularly effective for pools in formal settings. The drawbacks are that construction can be expensive and time-consuming. If cracks develop, concrete pools can be difficult to repair. Concrete must be treated or allowed to season before introducing fish or plants.

Clay: malleable

Lining pools with clay is an acceptable approach where there is underlying clay. The drawbacks are the difficulties in obtaining a sufficiently plastic clay uncontaminated with sand or stones and the degree of skill needed in applying and working the clay until it is completely free of air pockets and forms a uniformly deep cover (of not less than 15cm (6in).

Construction

The easiest way to mark out any proposed site is to lay rope or hosepipe to form the outline. Cut around the marker with a spade. Avoid extreme shapes and precise geometrical shapes unless the surroundings are formal.

Position marker pegs at equal intervals around the proposed pond. Set the first peg at the ideal level for the pond edge. Using a spirit level align the remaining pegs.

Excavate a hole to about 30cm (1ft) sloping the sides outwards by 20 degrees and level the bottom. Mark a marginal planting shelf about 30cm (1ft) wide and then dig out the central area to the desired depth.

If adding edging stones or bricks to the finished pond remove sufficient soil to a width of 30cm (1ft) all around the pond, so that the stones can be firmly bedded in.

 

Flexible liners

To calculate the size of liner required, measure the maximum length and width of the marked-out area. To each measurement add twice the depth, then allow an overlap of at least 15cm (6in) all round so that the liner can be held firmly by paving or tucked under turf. 

Commercially available underfelts should be used beneath liners. Fibreglass roll as used for loft insulation can also be used. On particularly stony soil a 1in (2.5cm) layer of damp sand can be put down first

Draw the liner over the hole and hold it in position with bricks. Let water from a hose gradually weigh down the liner into the hole, smoothly and with a minimum of creasing or wrinkling. To prevent stretching lift the bricks occasionally to allow the liner to move under the weight of water and mould itself into the contours of the pond. Fold in creases evenly. Cut off any excess liner, leaving a 15cm (6in) flap all around.

Vertical pool walls can be built, using bricks or concrete blocks, with butyl then used as an overall cover for walls and earthen pool bottom. To construct the walls lay footings of concrete with a smooth finish 15cm (6in) deep in the shape required. Then lay bricks or blocks in the normal way until the required height is reached.

Pools can be stepped into with reasonable care, and have stones or pebbles laid in them to create a beach or similar feature. They will also take breeze and concrete blocks wrapped in polythene or set on offcuts of butyl to hold up plant containers at a higher level instead of building concrete ledges within the pool.

Preformed rigid liners

Level the site and stand the mould the right way up, supported on bricks.

Mark out the contours with long canes pushed vertically into the ground and string around their base.

To dig a hole that matches the mould, first remove soil down to the level of the marginal shelf.

Place the pond liner in the prepared hole and press it down firmly onto the earth to leave a clear impression of the base.

Lift out the mould, then dig out the central, deeper area, allowing about 5cm (2in) extra depth for cushioning material.

Clear any stones, roots or debris from the hole. Tamp the soil firmly and line the excavation with pond underlay or a 5cm (2in) layer of damp sand.

Put the mould in place and check, using a spirit level, that it is level all the way round. Ensure the pond sits firmly on the bedding layer. Insert batons to hold it in place. Add about 10cm (4in) of water. With sand backfill around the sides to the same depth as the water ensuring there are no gaps and that the pond remains absolutely level.

Continue this process of adding water, backfilling and checking the level. Ensure the sand is well rammed beneath the shelf

Concrete Ponds

The most common way to construct a concrete pond is to use concrete walling blocks for the sides. These are skimmed with cement mixed with sharp sand and a fibrous reinforcing material.

Alternatively, a pond can be constructed from shuttering and poured concrete but shuttered ponds are prone to cracking.

Excavate the pool area, allowing an extra 15cm (6in) all round for the sides and 15cm (6in) extra at the base, to accommodate the thickness of the concrete. 

For larger pools, concrete may need reinforcing and expert help is advisable. Plan construction so that the actual laying of the concrete floor and the pouring of the concrete into the wall shuttering is completed in one day, to ensure that the finished pool is waterproof.

In winter cover all concrete surfaces against frost for four days. In summertime water the concrete and shuttering. The setting of concrete is a chemical reaction and the slower the concrete sets, the harder it will be and the more resistant to cracking.

The supports can be removed two days after concreting, and the shuttering removed from four days afterwards.

Soften and round the sharp edges of the concrete with a concreting trowel.

Whatever method of construction is used, sweep out the pool to clear it of all bits of concrete and cement dust and paint the inside surfaces with a proprietary neutralising and waterproofing sealant to prevent lime leaching out into the water.

Pond edging

For a  formal pond, place paving slabs around the pond on a bed of mortar (3 parts sand to 1 part cement) ensuring that there is a 5cm (2in) overlap over the pond to hide the liner. It is important that the paving slabs are level around the pond as any variation will be obvious against the water level. The mortar should be used to trap the pond liner and hold it in position. Immediately remove any mortar that falls into the pond. Complete the paving, ensuring that it is level, and allow it to set for 2 days before walking on it.

For an informal pond use natural-looking cobbles and stones around the edge of the pond, ensuring that the liner is completely covered and that it is above the water level. Natural paving stones can be used to secure the liner, placing them on a bed of mortar (3 parts sand to 1 part cement) and gently firming them into position.

Pond Equipment

To create a balanced, healthy pond, which looks good and provides a suitable home for fish and wildlife, it is important to have a pump as this is the heart of the pond, and responsible for any water movement and  you need it to run a filter system, watercourse, fountain, water feature etc. Areas of water movement and splashing are great for increasing the oxygen content of the pond and keeping it healthy. The type of pump you need will depend on what you want to do with it so ask the advice of your local garden centre or aquatic supplier

                                       pump

Filters

The fish and other inhabitants of your pond are constantly producing waste. This includes solid and dissolved wastes, both of which will cause problems if allowed to accumulate. Whilst very lightly stocked ponds, with plenty of plants, may remain in a natural balance, the vast majority require additional help to keep the water healthy. A filter provides an area in which natural waste removal can occur, thereby keeping the pond and its inhabitants healthy.

Ultraviolet clarifier

Although not essential, an ultraviolet clarifier is beneficial to most ponds. It prevents the formation of unsightly green water, thereby helping to keep the pond water crystal clear. Many filters come with integrated ultraviolet clarifiers

Filling your Pond with Water, Plants and Fish.

Water

Having constructed your pond and installed the equipment, you need to fill it with mains water. Rainwater and water treated with a domestic softener are unsuitable, as they lack essential minerals. Once its full of water treat it with a product that neutralises chlorine and other substances and makes its safe for fish and other pond inhabitants. Turn on all the equipment and leave your pond to settle for a week before adding plants and If you want to add fish wait another six weeks until the plants are established.

Plants


 iris  water lilly


Most ponds benefit from having a healthy selection of plants, both for their attractive qualities and for their positive effects on the pond environment. They attract wildlife, providing food, shelter, and breeding sites as well as adding colour to the pond, and breaking up hard edges. They produce valuable oxygen, and remove carbon dioxide. They shade the pond, providing cover for the fish and preventing excessive algae growth. They remove nutrients from the water, improving its quality and helping to prevent algae. Choice of plants include oxygenators that as the name suggest produce oxygen, marginal plants that come in all shapes and sizes, from tall grasses and irises to low, creeping varieties. They can provide shelter from the wind  and a safe refuge for all manner of pond life and plants like water lilies and other lily-like plants that grow in deeper areas of the pond, sending up leaves to the surface. These floating leaves are ideal for shading the pond, and fish will often bask under them on hot, sunny days. You should aim to cover around a third to one half of the pond with floating leaf plants.   


aquatic     aquatic photo   


Fish

Having filled your pond, turned on the equipment, and stocked it with plants, you can now turn your attention to stocking it with fish. This is one of the most enjoyable parts of creating your pond and should be done carefully. A  very common mistake made in new ponds is to stock the fish too quickly as this can lead to sick fish and disappointment, caused through poor water quality – a phenomenon known as ‘New Pond Syndrome’. In a ‘mature’ pond, the filter contains a population of bacteria that convert the ammonia that fish excrete into nitrite, and then turn nitrite into nitrate. Both ammonia and nitrite are toxic to fish and other pond life, and they must be turned into nitrate for a healthy environment so it's important to introduce fish a few at a time.

      fish koi pond2 

When all the hard work is complete your pond should then just need some annual maintenance to keep it healthy, like cleaning, trimming back overhanging branches or dividing and thinning out of plants.

  • Autumn The best time to clean ponds is in late autumn when many creatures are less active and you can just remove any debris build up or weeds
  • Summer - Water evaporates during windy or hot weather, leading to the water level dropping. The reduced surface area can be damaging to fish as there’s less oxygen available, so top up the pond if necessary and for a top up you can use rainwater
  • Winter If the pond is stocked with fish and it does freeze over, melt the ice by placing a hot pan on the surface or install a pond heater or water feature to prevent freezing occurring. Floating a ball on the water in cold weather can also delay freezing. Never smash the ice, as the shock waves can harm fish Improving the oxygen levels in the water by circulating it with a pump benefits both amphibians and fish, particularly in deeper ponds where oxygen does not diffuse readily through the water.

 

Posted by Charlie Groves

Charlie is the manager at Groves Nurseries.  He is the 6th generation of C.W. Groves to run the garden centre. 

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