While water in a garden can create an air of peace and tranquillity, fish can provide extra character and movement and will quickly learn to respond to their owners, although it isn't a great idea to tame them.

However, you can't just pick out a pretty one from an aquatic centre and take it home and hope for the best. There are several important considerations before you begin.

Firstly, the pond needs to be of an adequate size to accommodate the fish and give them the best chance of survival. The rule of thumb is to allow 1cm of fish body length for every 60 sq cm of pond surface.

The pool also needs an area at least 75-110cm (30-39in) deep which will remain ice-free, giving the fish a resting place in winter. If you're hoping to keep koi carp, this area will need to be deeper - around 1.2m (4ft).

The most obvious choice for a small pond is the common goldfish. Go to a reputable aquatics centre and select fish which are small and compact, look alert and active, are swimming well and not looking listless or unhealthy. Avoid those with torn fins, fluffy growths or blood stains on them.

More exotic goldfish, such as twintails and fantails, do better in aquariums rather than ponds. Golden orfe are surface swimmers and need a pond at least 3m (10ft) long as they may jump out of smaller ponds if startled. They make excellent display fish, but grow quite large so are not suitable for smaller pools. Other suitable fish for ponds include shubunkins and golden comet.

If you have a larger pond, you can consider keeping koi, an ornamental species of carp, much prized by the Japanese for their exotic colouring and marking. Always buy koi only from a reputable source and make sure that your garden is secure, as large or well-coloured specimens are extremely valuable.

When you are creating a new pond, make sure the plants are established and the water is clear and balanced before introducing any fish. A six-month period will allow the water plants to grow, providing some shade and a few hiding places, while the oxygenating plants have time to become established.

Floating foliage will give fish shade and cover from herons and other predators, while all the plants in and around the edges of the pond take up fish waste matter with their roots and help to keep the water in good condition.

Suitable plants for ponds include iris, nymphaea, Acorus calamus and Butomus umbellatus. Canadian pondweed is good for the water if you have fish, as it's an evergreen which keeps oxygenating the pond all year round and you don't need to plant it.

Bunches are sold weighted down at one end and will root into the debris which builds up in the bottom. However, it is invasive and will need to be thinned out several times in the summer to stop it taking over.

Let fish acclimatise to the water gradually. It's a good idea to let them float in a plastic bag on the surface for an hour until the water adjusts to pond temperature and then open the bag and let them swim out.

Pond fish are cold blooded and the amount of food they need depends upon their activity, which is closely tied to the water temperature. Goldfish and koi become very sluggish below 8-10C and it is generally best not to feed them when daytime temperatures fall below 10C or if there is any night-time ice on the pond.

Feeding at too low a temperature can result in food being uneaten and polluting the water.

Even when it is mild enough, feed only lightly until warmer weather arrives. Special foods are available for cool weather feeding that are more readily digested. Follow the manufacturer's recommendations on when to feed and use a pool thermometer if necessary to monitor water temperature.

Feeding during the milder days of autumn can help to build fish up for their winter 'down time', and feeding in the warmer days of spring will help them to recover from the winter. When really cold weather finally arrives, it is best to stop feeding altogether.