The Saim Aquarium Decor Pirate Skeletons & Gold Treasures Air-Driven Action Moving Up-and-Down Skeleton Halloween Aquarium Ornaments are perfect for adding some fun to your aquarium setup. These air-driven ornaments move up and down in a real, mechanical fashion, providing entertainment for your fish as they swim around. They also require no additional equipment for operation, making them easy to set up and use.