The Polypterus senegalus, commonly known as the Senegal bichir, gray bichir, or dinosaur bichir, is a fascinating freshwater fish native to various parts of Africa. Belonging to the ancient Polypteridae family, this species possesses a distinctive, elongated body and armor-like scales that give it a prehistoric appearance, often leading to its “dinosaur” moniker. Its unique physical features and ancient lineage make it a captivating addition for many aquarium enthusiasts. This species is frequently kept in the aquarium hobby due to its manageable size and hardy nature.
Aquarium Setup and Habitat
Providing an appropriate aquarium environment is important for the well-being of a Senegal bichir. These fish, reaching up to 14-16 inches in captivity, prioritize floor space over tank height. A minimum tank size of 55 gallons is recommended for a single specimen, though a 75-gallon or larger tank with a long footprint is preferable to accommodate their movement. The most important aspect of their habitat is a heavy, tightly fitting lid, as these fish are notorious escape artists. It is also advisable to leave a small gap between the water surface and the lid to allow them access to atmospheric air.
Water parameters for Polypterus senegalus are adaptable, but stability is important. An ideal temperature range is 75-82°F (24-28°C), while the pH should be maintained between 6.0 and 8.0, with a hardness level of 5-20 dGH. A soft, fine substrate like sand is recommended to protect their delicate undersides as they spend most of their time at the bottom. Including ample hiding places such as driftwood, smooth rocks, and caves provides security and reduces stress for these nocturnal fish. Dim lighting can enhance their comfort, mimicking their natural habitats.
Diet and Feeding
The Polypterus senegalus is a carnivorous species, requiring a protein-rich diet. While some keepers report success with high-quality sinking carnivore pellets or wafers, these typically serve as a supplementary food source rather than a staple. The bulk of their diet should consist of frozen foods such as bloodworms, mysis shrimp, krill, and chopped fish or prawns. Earthworms are also a nutritious option.
Live foods can be offered, but they carry risks of introducing diseases or parasites. Bichirs possess poor eyesight and primarily rely on their keen sense of smell to locate food. They are generally slow feeders, so it is important to ensure each fish receives enough food, especially if kept in a group. Offering food during their nocturnal hours or dimming the lights can encourage feeding behavior.
Behavior and Compatible Tank Mates
Senegal bichirs exhibit a semi-aggressive and predatory temperament. They are opportunistic carnivores that will attempt to consume any fish or invertebrate small enough to fit into their mouths. Careful consideration is needed when selecting tank mates. Despite their predatory nature, they are not typically aggressive towards species too large to be considered prey.
Suitable tank mates are other bichir species of similar size, larger peaceful cichlids like Oscars or Silver Dollars, Synodontis catfish, and larger characins such as Congo Tetras. Fish to avoid include small, schooling species like neon tetras, guppies, or small shrimp, as these will be viewed as food. Avoid highly aggressive fish that might bully the bichir, or certain pleco species known to damage the bichir’s slime coat.
Unique Biological Traits
The Polypterus senegalus possesses unique biological adaptations that underscore its ancient lineage. A remarkable feature is a modified swim bladder that functions as a primitive lung. This adaptation allows the bichir to breathe atmospheric air from the surface of the water, a behavior often observed in the aquarium. This ability is useful in their natural habitats, which can experience low oxygen levels.
Another trait is their method of locomotion. While capable of swimming, Senegal bichirs use their pectoral fins to “walk” or push themselves along the substrate. This movement, resembling a terrestrial gait, highlights their evolutionary history. Their robust, ganoid scales provide armor-like protection and contribute to their “living fossil” designation.