The Coral Red Pencilfish, scientifically known as Nannostomus mortenthaleri, is a highly sought-after species in the aquarium hobby, renowned for its vibrant coloration and elegant swimming behavior. Native to the freshwater habitats of Peru, particularly in the Amazon Basin, this small and slender fish is part of the Lebiasinidae family and is distinguished by its striking red and black bands that run horizontally along the length of its body, creating a vivid contrast that captivates onlookers.

Nannostomus mortenthaleri thrives in environments that replicate the calm and shaded waters of its natural habitat. To create a suitable aquarium setting, it's advisable to include dense plantings of both submerged and floating aquatic plants, which provide the fish with hiding spots and mimic the densely vegetated waterways they are accustomed to. A dark substrate can enhance the fish's coloration, while soft, slightly acidic water conditions reflect the typical characteristics of their native environment.

The diet of the Coral Red Pencilfish is omnivorous, with a preference for small invertebrates and zooplankton in the wild. In captivity, they should be provided with a balanced diet that includes high-quality flake foods, micro pellets, and live or frozen foods such as daphnia, brine shrimp, and bloodworms. Offering a variety of foods not only ensures they receive all the necessary nutrients for optimal health but also encourages their natural foraging behaviors.

Breeding Nannostomus mortenthaleri can be a delicate process but is certainly achievable with careful attention to water conditions and diet. They are egg scatterers, releasing their eggs among fine-leaved plants or a spawning mop. To encourage spawning, 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 the Coral Red Pencilfish 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, Nannostomus mortenthaleri, or the Coral Red Pencilfish, offers aquarists the opportunity to keep a small, peaceful, and strikingly beautiful species that adds both visual interest and elegance to the freshwater aquarium. While their care requires attention to their dietary, environmental, and social needs, the rewards of keeping Coral Red Pencilfish include the enjoyment of their vivid coloration and the serene beauty they bring to the aquatic setting.