Koi carp ponds - review

A Koi pond is designed specifically for keeping (Japanese) Koi carp. Koi can live in normal garden pond, with lilies or other plants, but Koi owners tend to want bright clear water in order to view their treasured fish. The water most also be healthy for the fish. Typical design criteria:at least 2,000 litres (500 gallons) but 'the bigger, the better'

• at least 600mm (24") deep
• vertical walls, to provide depth and discourage predators
• a bottom drain, so that the pool can be emptied and cleaned when necessary
• a pool floor which slopes towards the drain outlet
• a biological filtration system (not a filter system designed for a bathing pool)