Abstract: A floating island for an aquarium according to the invention includes a board-shaped floating island body, a supporting rod and a fixing device. One or a plurality of the supporting rod are slidably inserted in the floating island body in the direction of the thickness of the floating island body. The supporting rod is fixed in un upright state in an aquarium by a fixing device. The floating island body can stably stay on the water by the supporting rods, and can also automatically move up and down in accordance with the change of the water level.