The ponds are constructed by two types namely, dug out and embankment pond. The dug out pond is constructed by digging the soil and is most suitable to construct ponds in plain areas. It is to be scientifically constructed maintaining shape, size, depth and other factors. A pond for goldfish or water lilies need be only about 2 feet deep for zones 5 or greater. Ponds built in colder areas may need more depth to keep the pond from freezing solid. Ponds built for koi should be 3 feet or deeper to allow these larger fish enough space.