Abstract: An aquarium-terrarium ecosystem with both a containing area and a body of water is formed from a bottom section, a plurality of side plates, a concave shaped midsection, and a top section. The bottom section has at least three side edges. Each one of said plurality of side plates is attached to one of the side edges of the bottom section. Each one of the plurality of side edges extends substantially vertical from said bottom section. The longitudinal edges of each one of said plurality of side plates are connected to adjacent longitudinal side edges of adjacent side plates to form a polyhedron for containing a body of water. The polyhedron has a top edge. The concave midsection has both a forward and rear edge. The midsection is connected to at least a portion of the top edge of the polyhedron to form a separate containing area apart from the body of water. The forward edge of the midsection partially extends into the polyhedron to form an interface between the body of water and the separate containing area.