Goldfish are the world's most popular pet fish. They can be kept in both ponds and aquariums with ease as long as the appropriate care is taken. Like other ornamental varieties, the Goldfish has been bred in many different, attractive, and mixed colour forms. With the common Goldfish, their body size and shape is usually well proportioned with a short tail. They can grow to around 20 to 25cm in length (excluding the tails) although this does depend on habitat size, feeding and general husbandry.