Known artificial habitats in polyhedron form for crustaceans on aquatic soft floors having independent stability and structured surfaces either have an extremely small structure at the transition to the aquatic soft floor or no such structure. However, crabs are hard floor animals and settle in soft floors only under hard components. The artificial habitat (01) according to the invention is therefore characterized by a symmetrical solid body (02) in tetrahedron form with four identical sides (03), each forming a possible standing surface (04) and in the surfaces (07) of which three channel-shaped main passages (06) are arranged extending along the median (22) from the side edge (08) as far as a common intersecting point (09) in the side centre of gravity (10). As a result, the solid body (02) in tetrahedron form constitutes a particularly attractive artificial habitat (01) for crustaceans because the latter are provided with main passages (06) as entry aids (11) and with initial cavities and sufficiently large surfaces (07) in the sides (03) of the solid body (02), which can preferably be used by the crustaceans for building cavities (12) for themselves below the solid body (02). Connecting passages (19) make it possible to save on material, for example lightweight concrete, and to achieve better handling, additionally also in uses as a fishing block or pond protector.