The Copper Harlequin, scientifically known as Trigonostigma espei, is a vibrant and captivating species of freshwater fish that belongs to the same family as the more commonly known Harlequin Rasbora. Native to Southeast Asia, particularly in Thailand and parts of Cambodia, this small and peaceful fish is highly valued in the aquarium hobby for its striking coloration and ease of care, making it an excellent choice for both novice and experienced aquarists alike.

Trigonostigma espei is characterized by its bright, copper-orange body which is beautifully contrasted by a distinctive black, wedge-shaped patch near the tail. This marking, along with its shimmering color, makes the Copper Harlequin a standout addition to any freshwater aquarium. They are relatively small, making them suitable for a variety of tank sizes, but they truly thrive and display their best behaviors and coloration when kept in groups, as they are naturally schooling fish.

Creating an optimal environment for the Copper Harlequin involves mimicking their natural habitat as closely as possible. The aquarium should be densely planted with a variety of aquatic plants, providing ample hiding spots and replicating the densely vegetated waterways of their native environment. Soft, slightly acidic to neutral water conditions, along with a gentle current, will help simulate the streams and pools where these fish are found in the wild. A dark substrate can further enhance their stunning copper coloration.

The diet of Trigonostigma espei is omnivorous, with a natural preference for small invertebrates and plant matter. In captivity, they should be provided with a varied diet that includes high-quality flake foods, micro pellets, and live or frozen foods such as brine shrimp, daphnia, and bloodworms. This varied diet helps ensure they receive all the necessary nutrients for optimal health and vibrant coloration.

Breeding the Copper Harlequin can be a rewarding experience. They are egg scatterers, releasing their eggs among the fine-leaved plants. To encourage breeding, a separate breeding tank with optimal water conditions and plenty of plant cover can be beneficial. The fry are small and should be fed infusoria or other fine foods until they are large enough to accept larger fare.

Caring for Trigonostigma espei involves regular maintenance to ensure the water quality remains high, with frequent water changes and effective filtration. Their peaceful nature makes them excellent candidates for community tanks, where they can be kept with other similarly sized and non-aggressive fish species. However, their schooling behavior and preference for swimming in groups should be considered when planning tank size and composition to ensure a harmonious environment.

In summary, Trigonostigma espei, or the Copper Harlequin, offers aquarists the chance to keep a small, peaceful, and beautifully colored species that adds both movement and visual interest to the freshwater aquarium. While their care requires attention to their dietary, environmental, and social needs, the rewards of keeping Copper Harlequins include the enjoyment of their striking appearance and the dynamic presence they bring to the aquatic setting.