Creepy Skull Castle Aquarium Ornament from Aqua One Add some dimension and life to your aquarium with Aqua One’s designer lifestyle ornaments! You are sure to find an ornament that will suit your aquarium and style. The Skull Castle from Aqua One will add an element of interest to any aquarium whilst providing your fish with places to hide, explore and even breed. Combine with other ornaments, plants and backgrounds to create a medieval environment for your fish to explore and a unique panorama for your viewing pleasure.