Abstract: The present relates to an aquarium drainage assembly comprising a pipe member having an inner nipple adapted to be mounted within a designated opening formed in a wall of the aquarium and an outer nipple extending outside the aquarium. The inner nipple is permanently mounted within the aquarium by a locking nut mounted on the pipe member, the locking nut being adapted to tightly clamp the assembly to the wall. A sealing element is located on the pipe member and placed around the opening adjacent to an inner and an outer surface of the wall; it permits a watertight sealing of the assembly within the opening. A valve element mounted within the outer nipple allows to regulate water circulation through the assembly. The locking nut includes a thread which is tightened around the inner nipple via a corresponding thread formed around an outer surface of the inner nipple and a stopper located on the outer nipple.