Bichirs are fish from the Polypteridae family, and they're a sister group of ray-finned fishes. They have developed similar characteristics like two functional lungs, as well as Ampullae of Lorenzini - organs that can sense electricity or electroreceptors. It is worth noting that there are about 12 species in this genus recognized as Bichirs all living in freshwater systems found only in Africa's tropics.
These large and aggressive animals need tanks with sufficient space to accommodate them; it is recommended for inexperienced aquarists because they require special attention due to their carnivorous diet and tank conditions (elements which may not be easy to fulfill). The specimens you encounter available on the market are caught mostly by fishing boats instead of being commercial bred (not many breeders exist yet).