The Rasbora Harlequin fish, also known as Trigonostigma heteromorpha, is a popular freshwater fish that is native to Southeast Asia, specifically Thailand, Malaysia, and Singapore. It is a small, peaceful fish that is known for its striking appearance. The Harlequin Rasbora has a sleek body with a bright orange-red coloration on its lower body, and a deep black patch on its triangular-shaped upper body. This unique pattern gives it the name "harlequin." They also have a neon blue-green stripe that runs horizontally along their body, adding to their eye-catching beauty. In terms of care, Rasbora Harlequins are relatively easy to maintain. They thrive in a well-established aquarium with plenty of plants and open swimming space. They prefer slightly acidic to neutral water conditions, with a temperature range of 72-79°F (22-26°C). They are peaceful and social fish, so it's recommended to keep them in groups of at least six to eight individuals. In terms of diet, Harlequin Rasboras are omnivorous and will accept a variety of foods. They primarily feed on small insects, worms, and crustaceans in the wild. In an aquarium, they can be fed a combination of high-quality flakes, pellets, and frozen or live foods such as brine shrimp or bloodworms. Overall, Rasbora Harlequins are a great choice for beginner aquarists due to their peaceful nature, stunning appearance, and relatively easy care requirements. They can be a beautiful addition to a community aquarium, but it's essential to ensure proper tank conditions and compatible tank mates to maintain their well-being.