The Natural Pond
Well-designed wildlife ponds should have easy access for small animals and shallow areas for bathing and drinking. When using a liner a shallow bowl-shaped cross-section is ideal, with a depth of 60cm / 24 inches adequate for overwintering life. Species such as the common toad and the legally protected great crested newt favour deeper ponds and can be hard to tempt to new habitats. For most species, shallow areas that warm up quickly in Spring are a key factor. Larger pools are generally more attractive to wildlife but any size will quickly attract life.
Small pre-formed pools can be used and are frequently designed with wildlife in mind. Where these feature steep sides, some careful planning may be necessary to enable access and prevent visiting garden animals such as hedgehogs from drowning.
The best wildlife ponds feature native aquatic plants. These are readily available and in many cases very attractive as well as providing the right habitat for native insects. Some of these plants can be rather rampant and prone to taking over a small pond. A good book on pond plants can reveal which species are best avoided in a restricted space. Non-native species can be added but avoid invasive plants such as New Zealand Stonecrop (Crassula Helmsii) & other aggressive aliens.
Although many sources advise adding a layer of soil to the pond, this can often lead to nutrient problems and algae blooms. For this reason, confine plants to aquatic baskets and if you wish to add a substrate, silver sand is a better choice as it is inert and nutrient free. Using tap water can also add phosphates and other nutrients that can cause green-water or blanketweed blooms. Rainwater is a better option for the wildlife pond. Duckweed can be a nuisance if allowed to establish itself and will quickly shade all life in the pond if not removed by hand.
The limiting factor of most ponds is the presence of fish. Although adding to the beauty of the garden, most fish will eat important invertebrate life and insects that serve to keep a wildlife pond in good shape. In the absence of fish water fleas (Daphnia) will consume green-water algae and help maintain clear water. Fish will also make a meal of tadpoles and newt larvae. As in nature, fish can be part of a balanced community in larger ponds but given the lack of pumps and filtration are best avoided in smaller scale set-ups. Where appropriate Golden Rudd (Scardinius erythropthalmus) are the best choice and are a domesticated form of a native species. Small fishes such as Sticklebacks (Gasterosteus aculeatus) can be very efficient predators and Minnows (Phoxinus phoxinus) require moving water to thrive.
Why not build a wildlife pond?
Every garden benefits from a water feature and even the smallest pond can attract wildlife.
Given the loss of wild habitats, garden ponds have become increasingly important to wildlife and have saved amphibians such as Frogs and Toads from disappearing in many areas.
Although many animals will visit a variety of water features, a well-designed wildlife pond will attract a wide range of native creatures and enable them to thrive and reproduce, to the benefit of both garden and gardener. Frogs and Toads will help control Slugs and Snails, Dragon Flies have a hearty appetite for mosquitoes and other small flying-insects and garden birds will benefit from somewhere to drink and bathe.