Decorations can be moved across aquariums by using the store 🏪
1. Select a decoration to open the menu below it 🔘
2. Choose the box icon in the menu, and the decoration will disappear from the aquarium, and then appear in the Store tab 🗃️
3. Go to a different aquarium and open the Store 🥌
4. Stored decorations are marked Stored. Select the decoration, and in the next window choose Place 📍
5. Enjoy your decoration in its new environs 🏖️