Tips on how to give fish the best start in your pond - plus, find out what else needs doing in the garden this week.

By Hannah Stephenson.

If you've ever walked past an ornamental lake and marvelled at the fish in the water, perhaps it's time to introduce some fish into your own pond.

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.

Best of the bunch - Dicentra spectabilis These elegant perennials with fern-like leaves and heart-shaped blooms on arching stems are extremely easy to grow and flower early, peaking in May.

The taller types make good planting companions with mossy saxifrages, ivies and hellebores, while other good plant partners include hardy geraniums and hostas, or other plants providing interest later in the season.

Smaller dicentras can be grown with foxgloves, tall campanulas and astilbes. They will thrive in sun or shade and in most soils but they do best in sheltered spots in semi shade and a moist soil.

If you keep them out of the midday sun and keep the ground moist, you may extend the flowering season into the summer. D. spectabilis, which is widely available, will grow up to 90cm (3ft) tall, producing arching sprays of pink flowers, while 'Alba' is shorter, at 70cm (28in), with ivory white flowers. The more compact dicentras, growing up to 45cm (18in) high, include 'Snowflakes' and 'Bacchanal'.

Good enough to eat - Creating a herb garden You don't need masses of space to grow a selection of herbs which will add flavour to your meals virtually all year round, but you will have to make sure that the herbs you grow together will have the same growing requirements.

Many herbs don't like the moisture-retentive rich soil preferred by vegetables, so you may want to give these a separate space, in the form of a herb wheel or simply some large pots in which they will thrive in the right conditions.

Not all herbs like full sun. Thyme, sage, rosemary, French tarragon and oregano like it hot; rocket, sorrel, mizuna, mustard, parsley and chervil prefer partial shade.

Parsley prefers cool light shade, chives thrive in rich soil, while mint prefers plenty of moisture.

Some are shortlived and need successional sowing through the season, including basil, coriander and parsley, while others will survive for a long time in a pot, such as marjoram, mint, chives, sage and thyme.

If you are planning a herb garden as a central island in the lawn, put the tallest herbs in the middle and the lower-growing ones on the outside. For a garden in an established border, the tallest plants go to the back near the fence, and the lower ones in the front.

A wooden barrel or large terracotta pot planted with trailing thyme, chives, sage, basil, coriander, tarragon and with French lavender in the middle looks very effective. Even in the smallest space - whether just a windowbox or hanging basket - you could grow a selection of fragrant herbs, making sure what you plant is suitably located.

Three ways to... Renovate a pond 1. Remove all planting baskets, divide overcrowded plants and repot after washing everything well in clean water.

2. Empty as much water as you can out of the pond, either using a submersible pond pump, or making a syphon with a hosepipe, or simply bailing it out with a bucket.

3. Clean out all but 5cm (2in) of silt from the bottom, removing rotting debris, before refilling it and replacing the planting baskets.

What to do this week :: Deadhead violas and pansies to prolong flowering.

:: Guard plants against slugs and snails, which will feast on the young shoots of flowering plants and vegetables.

:: Pinch out the growing tips of dahlias to encourage branching.

:: Cut back penstemon. Doing this late in the season means that the new growth will be less likely to be damaged by frost.

:: Repot greenhouse tomatoes when they outgrow their pots and pinch out sideshoots, which can then be treated as cuttings.

:: If you haven't yet done it, plant up your hanging baskets but keep them sheltered at night if frost is forecast.

:: Continue to harvest Oriental greens, first new potatoes and radishes.

:: Remove raspberry suckers in your rows of raspberries.

:: Keep onions well watered or the bulbs will stop swelling.

:: Hoe between vegetable rows to keep down weeds.

:: Plant out greenhouse-raised leeks, broad beans, peas and lettuces.

:: Continue to remove faded flowerheads from daffodils but don't cut down the foliage until at least six weeks after deadheading.

:: In the greenhouse, remove male flowers from cucumber plants before they open. Male flowers don't have a small swelling at their base, whereas female flowers do.