Pool Comets / Goldfish
Commonly known as goldfish, they come in assorted varieties like Koi, such as fantails, orandas, shubunkins, or the common pool comet (the little plain ones you win at the fair). They can grow up to 12 inches in length and live up to 20 plus years. They can inhabit a pond with Koi and both will live peacefully with each other. Smaller ponds (garden ponds/water gardens) are ideal for these little guys.