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About pond care

The key to a healthy pond is keeping the water clear and ensuring that plants do not take over. If you have the right balance of plants and oxygen, you will encourage wildlife and your aquatic plants will thrive.

Common pond problems

Water loss

• There can be several causes of persistant water loss in a pond, many of which are due to problems at the building stage. If you're losing water, check first that the pond's edges are level, as water may be overflowing at the lowest point. If the water level in a lined pond drops or the flow of water decreases, check that no part of the liner has slipped below the water level.
• If a pond is leaking, it needs to be drained and inspected. Before draining, transfer any fish and plants into a suitable container which should be kept in the shade. The quickest way to drain is with an electric pump - these can easily be hired.
• If your pond has a butyl liner, leaks may be caused by punctures. The easiest way to repair this is with double-sided adhesive tape which can be used to secure a patch of butyl liner over a hole. The pond can be refilled an hour after the tape secured the hole.
• If a fibreglass pond unit isn't well supported or the ground underneath is not properly consolidated, it may crack under the weight of the water. Cracks can easily be repaired with a fibreglass repair kit, as used for car bodies. Allow the compound to harden as it may be toxic when in liquid form. Before refilling the pond with water, make sure that the base is firmly bedded down and that the soil is compacted around the sides to support the water pressure.
• The most common cause of leaking in a concrete pond is through cracks created by winter frost damage. Inspect the surface carefully as cracks can be very fine. Brush them free of any debris before sealing the cracks with mortar. Leave it to dry and then paint it with a sealant.

Maintaining water quality

• Once a balance of plants and animal life is established, the water should remain clear without needing further attention. However, if you notice any changes in the numbers of fish and plants, the water balance may be slightly off and a surge of algal growth may result.
• As algae depend on sunlight, carbon dioxide and dissolved mineral salts for survival, reduce the amount of sunlight they receive by growing plants such as waterlilies. Grow sufficient numbers of plants so that their floating leaves cover more than 50 per cent of the water surface.
• The addition of oxygenating plants, which are efficient at absorbing minerals and carbon dioxide, helps to starve out the algae. It's important to remove any rotting organic matter in the pond such as dead leaves and flowers. A form of algae known as blanketweed is often found in ponds, and if left unchecked can choke the plants and restrict the movement of fish. Make sure you remove blanketweed periodically by lifting it out with a garden rake.

Plant care and pest control

• Aquatic plants don't require much attention, but periodic division helps keep them healthy. Every couple of years, in late spring or early autumn, divide plants that are overgrown or crowding neighbouring plants. Thick roots may need to be divided with a spade or a knife and divided clumps can be replanted singly.
• Pests are less of a problem in ponds with fish, as the fish eat the insect larvae. In late summer aphids often attack water lilies and other aquatic plants, causing discolouring and decay. Use a hose pipe to wash away the aphids, or submerge the leaves of plants for 24 hours.

Autumn and winter maintenance

• The most important task in autumn is to keep the water free from decaying vegetation. Remove dead and dying foliage regularly and prune back excess growth of submerged plants. Place netting over the pond where practicable as this can help autumn maintenance by keeping leaves and debris from falling in and fouling the water.
• During the winter months ice may form, trapping methane gas which is released from submerged decaying vegetation and is potentially lethal to fish. Ice also exerts excess pressure on the sides of concrete ponds, often causing them to crack. Ensure that the pond remains free of ice by floating a ball on the pond's surface, or use an electric pool heater. This gives out just enough heat to maintain a small area of open water.

Five water plants to try

• Nymphaea 'Gonnere' - waterlily with scented white flowers
• Nymphaea 'Pygmaea Helvola' - dwarf waterlily good for smaller ponds with bright yellow cupped flowers
• Butomus umbellatus - a flowering rush with distinctive umbels of pink flowers on metre-long stems
• Iris laevigata - Japanese water iris - Lovely white iris that likes to grow in shallow water
• Pontederia cordata - free spreading marginal plant with spikes of blue flowers at the end of summer