Describe the annual maintenance of a garden pool including possible controls for algae including blanket weed.

Seasonal maintenance tasks to include: Water/vegetation balance, role of oxygenator plants; maintenance of water levels in summer; control of vigorous growth and invasive pondweeds, division of plants; netting against leaves, management of ice formation.

MAINTAINING A WATER GARDEN

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.

Remove thick layers of algae during the first months of the pond being planted/constructed (in spring/summer) and any large area of blanket weed annually.

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.

OXYGENATOR PLANT Submerged plants (aka oxygenators) Submerged plants produce oxygen during the day and provide cover for aquatic life Oxygenating plants can be purchased in bunches and are planted into baskets. They will need anchoring firmly in place. Approximately four to five bunches, each containing three to four stems, per square metre of water surface should be sufficient. As these plants respire at night, too many can lead to a lack of oxygen at night during the summer, causing fish to die. Avoid invasive species such as Myriophyllum aquaticum (Parrot’s Feather).

POND WEED

POND NETTING

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

Controls for algae to include pond balance, use of barley straw or other additives and manual methods of removal.

ALGAE

POND ALGAE

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 Water Lilies. Grow sufficient numbers of plants so that their floating leaves cover more than 50% of the water surface;

POND BALANCE

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;

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 blanket weed is often found in ponds, and if left unchecked can choke the plants and restrict the movement of fish. Make sure you remove blanket weed periodically by lifting it out with a garden rake.