Ponds can be a focal point in a formal garden design or create a back-to-nature feel in a native or cottage-style garden.

Choosing a site
Water usually flows and collects in the lowest part of the garden, so your pond will look most natural there. If you plan to keep fish or grow waterlilies, your pond will need at least five hours of sun a day. If you want to add a filter in the water, you'll need to locate your pond near a power point.

Size and shape
Bigger, deeper ponds are better than smaller ones. Water evaporates quickly in small ponds, and fish and many plants don't do well in the fluctuating water temperatures. Having shallower water at the edge of the pond lets you grow marsh plants, but make sure that two-thirds of the pond's surface is at least 600mm deep. This protects fish from cats, birds and sunburn and allows you to grow deep-water plants such as waterlilies.

Building the pond
Decide on whether you're digging a lake or a pond and lay out your plan! If it's to be an irregular, natural-looking pond, use a long rope or garden hose to lay out the shape. If you prefer a more classic, square or rectangular pond, stretch a piece of string taut between stakes. Although it's easy to buy a ready-made fibreglass pond, this restricts your choice of size and shape. Concrete ponds tend to crack and leak, unless you're an expert concreter. The best option is a pond liner. Black plastic is cheap in the short term, but it punctures easily and will need replacing after a few years in the sun. The best liners are made from synthetic rubber (butyl rubber). It's expensive, but is guaranteed for 20 years and will probably last for 50. Larger nurseries and hardware stores may carry butyl rubber, but otherwise check with a water-garden specialist.

Here's how:
1. Lay out your pond's shape, scrape off 5cm of dark topsoil and keep it to spread over your garden. Dig out the pond, sloping the sides at a 45-degree angle. If you like shallow-water marsh plants, dig a shelf into your pond. As your pond could overflow in heavy rain, think ahead to where the water will run.

Slope pond's sides at a 45 degree angle.

2. Use a level to make sure the pond's outside edge is even all around. Clear the edges and bottom of anything that could puncture the plastic or rubber liner.

Make sure the pond's rim is level.

3. Add 50-80mm of sand to the bottom, then lay the liner in the hole and mould it to the pond's shape. A few wrinkles won't hurt! Secure the edge of the liner with bricks. Fill the pond with water. Leave the pond for a week to settle, and test for leaks. Hide the overhanging liner by digging a 150mm deep trench around the pond. Lay the liner in the trench, trim off the excess and fill the trench with soil, sand or cement.

Secure liner in place and fill pond. Trim excess liner.

4. Position pavers, rocks, bricks or timber around the edge of the pond.

Place edging around pond and position plants.

Source: Outdoor Structures (Murdoch Books)