Ornamental fish are a popular choice for aquariums and ponds, and two of the most popular species are KOI and IDE. KOI is a type of carp that is brightly colored and can grow up to 3 feet long. IDE is a species of freshwater fish native to Europe and Asia that is known for its silver-green coloration and long fins. Both species are popular choices for ornamental fish due to their attractive colors and interesting shapes.