Building a backyard fish pond is a big undertaking that involves a fair amount of hard work and, as it will be a permanent feature of your garden, it is worthwhile spending some time in the planning stage.

So before you rush into the garden with a shovel, pause for a while and think about your fish pond design and the type of pond that you want ...

Natural Pond - follows the curves and forms of nature and may include an outcrop of stone or a natural beach. This will often allow planting at the edge of the pool and can create the impression that the pond was there long before the rest of the garden or the house were constructed.

Formal Pond - a geometric design works best when there is a relationship in design and materials with the buidings that are close by. It will usually be symmetrical in design and could be rectangular or square in shape and may have a paved edge. Formal ponds are often planted but usually with artfully chosen plants rather than the wilder plantings of a natural pond.

Raised Pond - a formal pond can also be construced above ground from bricks, blocks or stone. There will be less waste to carry from the site, however the cost of the construction materials will be higher than an in-ground pond.

Once you've decided on the type of backyard fish pond spend some time working out possible locations and mark out the locations with a garden hose or a length or rope. Take into consideration the amount of light in different locations. If you want to grown water lilies you will require four to six hours of direct sunlight on the pond during the day. Shade is fine for fish-only ponds. Check the overhanging trees as these could also be a source of pond pollution. If you must build a pond beneath a tree at least try to avoid deciduous trees - the leaves will create a lot of pond waste.

When deciding on the location of your pond avoid the temptation to locate the pond in the lowest point in the garden. The low point can be subject to flooding in heavy rain and will often collect runoff from the garden. This may carry fertilizers and organic debris into the pond.

A pond for goldfish or aquatic plants need only be around two feet deep although more depth may be required in very cold areas to prevent the pond freezing in winter. If you want a koi fish pond it will need to be at least three feet deep or more.

The biggest mistake that water gardeners tend to make is to build a pond that is too small. Your finished pond will appear much smaller than your original layout!

If your backyard fish pond is to be dug out rather than raised consider how you will remove the excavated material. It may be possible to use it in another part of the garden, alternatively you may need to have it removed which can be difficult and expensive.

Assuming you are going to build a sunken pond the next step is to start digging! Dig the pond to the desired shape and dig a shelf around the perimeter of the pond about one foot deep and one or more feet wide. Dig the remainder of the pond. If you are planning a waterfall dig the pond with a slight slope away from the waterfall.

Line the excavated pond with underlay. This is to stop the flexible liner from being pierced by sharp stones. Pond underlay can be made from geotextile or old carpet, providing it is non-organic and non-rotting can be used to save money. A butyl rubber pond liner is laid on top of the underlay. Position to liner evenly in the pond and try to minimize the folds and wrinkles. Leave an overhang of at least six inches. Avoid walking on the newly laid liner as much as possible. If you must walk on it wear socks!

Fill the pond and try to ease the wrinkles out of the liner while the pond is filling. Arrange coping stones around the edge of the pond and fold the liner up behind the stones ensuring the edge of the liner is above the water level. A more natural edge can be created by planting shallow-water plants around the edge of the pond. You may need to consider cementing the coping stones in place if the pond edge will be subjected to much foot traffic.

Now sit back and enjoy your new garden pond!