Soil
The new pond should have a layer of subsoil or similar material to provide a habitat for pond organisms and a rooting zone for plants. This layer is necessary over concrete, flexible linings and newly-puddled clay. Clay is an inhospitable substrate for most organisms, and any plants that do root are likely to damage the clay lining.
Avoid using top soil, as this is likely to be nutrient-rich, and will release unwanted nutrients resulting in algal blooms and other problems. Normally the subsoil from the excavation should be suitable, but avoid using very stony subsoil or any that contains rubble or other debris. A layer about 100mm thick is suitable, but this can be varied to provide a range of conditions. The soil can either be spread before the new pond is filled, or can be sprinkled on the surface afterwards. Ensure that concrete is fully ‘cured’ before soil is introduced.
Soil can also be introduced in planting baskets, or by using some of the turves dug up during pond excavation. A turf can be tied to a marginal or submerged rooting plant, and then either placed or thrown into the water, where the turf will act as a rooting medium for the plants. Don’t use too many turves, because of the enrichment they may cause.
Reefs and beaches
Underwater reefs of stones or other material which leave gaps for newts, frogs, toads and other organisms provide a valuable habitat. Rounded stones can be placed in piles or ridges in deeper water, or leading up to beaches at the water ’s edge. Stones can also be used to retain the soil on marginal shelves. Use either large single stones, or smaller stones built up as a ‘dry’ stone wall. Bricks and blocks can also be used, but place them with plenty of gaps.
In deeper ponds, tyres can be used as reefs, and to make shelves or containers for planting.
Water quality
If the pond has a new concrete liner, test the water to check that the pH is suitable for the type of pond you require. Initially, water in any type of new pond will be turbid and may have scum on the surface, and will turn green as algae multiply. This will happen rapidly in warm weather. The water quality will improve as oxygenating plants and other organisms establish. Excessive algae growth in established ponds can be prevented.
