Introduction: Nothobranchius robustus is a captivating species of annual killifish known for its vibrant colors and unique life cycle. In this guide, we will delve into its taxonomy and classification, physical characteristics, habitat, distribution, tank setup, breeding, aquarium care, conservation status, and importance.

Taxonomy and Classification: Nothobranchius robustus is a member of the family Nothobranchiidae, which encompasses a diverse group of African and Madagascan killifish. The genus Nothobranchius consists of approximately 80 species, each with its own distinct characteristics. N. robustus, as the name suggests, is a robust species within this genus. Taxonomically, it is classified as follows:

• Family: Nothobranchiidae
• Genus: Nothobranchius
• Species: robustus

This species was first scientifically described in the 1920s and is native to East Africa, particularly the region of Tanzania. It is closely related to other Nothobranchius species but possesses unique features that make it a standout in the world of killifish.

Physical Characteristics: Nothobranchius robustus is distinguished by its vibrant colors, relatively small size, and elongated body shape. Adult males typically grow to be around 4-6 cm in length, while females are slightly smaller. Some of the key physical characteristics of N. robustus include:

1. Coloration: Adult males are known for their stunning and diverse coloration, which can include shades of red, blue, yellow, and green. Females are typically less colorful and often exhibit a more subdued appearance.
2. Fin Structure: These fish have elongated dorsal fins that run the length of their bodies, adding to their striking appearance.
3. Body Shape: N. robustus has an elongated and streamlined body, adapted for its agile swimming in the wild.

Habitat and Distribution: N. robustus is primarily found in the shallow waters of seasonal pools, swamps, and small streams in East Africa, with Tanzania being the primary region of its distribution. The species thrives in areas with a tropical climate that exhibits distinct wet and dry seasons.

During the dry season, N. robustus lays its eggs in the moist substrate of its habitat. These eggs enter a state of diapause, a form of dormancy that allows them to survive harsh environmental conditions. When the rainy season returns, the eggs hatch, and the young fish grow rapidly, completing their entire life cycle in a matter of months.

Tank Setup: Creating an ideal tank environment for N. robustus can be challenging due to their unique annual life cycle. Setting up a breeding tank is recommended to mimic their natural habitat. Here are some essential considerations:

1. Tank Size: A 10-gallon aquarium is suitable for a small group of N. robustus.
2. Substrate: Use fine-grained sand or peat moss to mimic their natural spawning substrate. Provide some spawning mops for egg deposition.
3. Water Parameters: Maintain a temperature between 24-28°C (75-82°F) and a pH level of 6.5-7.5. Keep water hardness relatively low.
4. Lighting: Offer a natural light cycle to regulate their breeding behavior and maintain a day-night rhythm.
5. Filtration: Utilize a gentle sponge filter to maintain water quality without creating strong currents that could disturb the fish.

Breeding: Breeding N. robustus can be a rewarding but somewhat complex process due to their annual life cycle. Here are the essential steps for successful breeding:

1. Pairing: Maintain a ratio of 2-3 females for every male in the breeding tank. Males will display their vivid colors during courtship.
2. Spawning: The fish will deposit eggs in the substrate or on spawning mops. Carefully collect these eggs to a separate container to prevent predation.
3. Incubation: Place the collected eggs in a separate container with a moist substrate. Ensure that the substrate remains damp but not waterlogged.
4. Diapause: Lower the temperature to around 20°C (68°F) to simulate the dry season. This temperature drop induces diapause, which lasts several weeks.
5. Hatching: Once the rainy season returns, raise the temperature and humidity to encourage hatching.
6. Rearing: Care for the young fish in a separate tank with appropriate water parameters, feeding them small live or frozen foods.

Aquarium Care and Considerations: To maintain a thriving aquarium for N. robustus, pay attention to their specific requirements:

1. Water Quality: Keep water parameters stable and conduct regular water changes to ensure the well-being of the fish.
2. Feeding: Offer a varied diet that includes high-quality flake food, live or frozen foods such as brine shrimp, daphnia, and mosquito larvae.
3. Compatibility: N. robustus is best kept in a species-only tank due to their specific requirements and territorial behaviors.
4. Observation: Monitor the fish closely, as they are known to be jumpers. Using a tight-fitting lid is crucial to prevent escapes.

Conservation Status and Importance: N. robustus, like many other Nothobranchius species, faces threats due to habitat destruction and climate change. Its limited distribution in Tanzania makes it particularly vulnerable to extinction. These fish play a vital role in the ecosystem by controlling insect populations and serving as prey for various birds and aquatic predators.

Conservation efforts are essential to protect N. robustus and other annual killifish species. Organizations work to conserve their natural habitats and study their unique life cycle to better understand and protect these fascinating fish.

In conclusion, Nothobranchius robustus is a remarkable species with its vibrant colors and annual life cycle. Understanding their taxonomy, habitat, and breeding requirements is crucial for their conservation and for those who wish to keep them in their aquariums. By providing suitable care and contributing to their protection, we can help preserve the beauty and diversity of N. robustus and similar killifish species.