an enclosure which defines an extension located both immediately above and rearward of an aquarium with a front wall , a rear wall , opposing side walls , a bottom wall , an open top . the enclosure comprising a fame that includes a plurality of support members . located about the frame members is a screen material or other material which defines the top , front , sides and rear walls of said enclosure . an opening is defined in the enclosure by the support members and the screen material . the opening is horizontally oriented , generally adjacent to the front wall and spaced below the top wall of the enclosure . the frame is adapted to be mounted relative to the aquarium such that the opening is generally coincidental with the open top of the aquarium . a portion of said enclosure is thus located above the aquarium with another portion of the enclosure located above and rearward of the rear wall of the aquarium . in this manner , the enclosure provides an enclosed space that extends both above and rearward of an aquarium so as to enable the healthy confinement of additional , principally land - based animals in a varied environment .