The term GOLDFISH RELATIVE refers to two species of fish, the CARP (4 letters) and the KOI (3 letters). CARP are a type of freshwater fish that are native to Europe and Asia. They have been introduced to other parts of the world, including North America, where they are now considered an invasive species. KOI are a domesticated variety of CARP that are kept as ornamental fish in ponds and aquariums. They are popular for their bright colors and patterns. Both CARP and KOI are related to goldfish, which are also a domesticated variety of CARP.