Gray bichir

The Senegal bichir is one of the most recognisable 'living fossil' fish in the hobby, representing a lineage that dates back to the Triassic period over 200 million years ago. Adults reach up to 70 cm standard length in the wild per FishBase, though captive specimens typically grow to 30–45 cm depending on tank size and feeding. The body is elongated and eel-like, covered in thick, armour-like ganoid scales, with a flattened head, external nostrils, and a row of dorsal finlets running along the back instead of a single continuous fin. Like all bichirs, Polypterus senegalus has a pair of lungs derived from the swim bladder and must have access to atmospheric air — it will drown if prevented from reaching the surface. A 200-litre tank is the minimum considered for a single adult, but a larger volume handles the waste load of this heavy feeder much better. The footprint matters more than height: a 120×45 cm base or larger suits their bottom-dwelling, horizontal swimming style. A tight-fitting lid is mandatory; bichirs are notorious escape artists. FishBase records a temperature range of 25–28°C, with a pH of 6.0–8.0. Senegal bichirs are nocturnal predators with poor eyesight but an excellent sense of smell. They will eat anything that fits in their mouths, including smaller tankmates. They are solitary by nature and do not need company of their own kind. Feed sinking carnivore pellets, earthworms, prawns, and pieces of fish. With good care they can live 15 years or more.