They're are absolutely safe for fish and best of all, they won't die, rot or cause any algae problems. When you connect the air pump tube,it can make air bubble,your fish can have fun with the air bubble. Offers the natural environment feeling.Change your aquarium into a beautiful scenery . Features: 1. It is vividly and color detailed to add lively and natural life to your tank. It is great to decorate your aquarium all the time with minimum responsibility and maintenance. 2. If you want the water wheel to rotate, you need to connect the air pump. (driven by the air pump above 2W) the air pump needs to be purchased separately . 3. Ornament is made from non-toxic plastic material and makes an exciting ornament in any aquarium. 4. They're are absolutely safe for fish and best of all, they won't die, rot or cause any algae problems. 5. When you connect the air pump tube,it can make air bubble,your fish can have fun with the air bubble. 6. Offers the natural environment feeling.Change your aquarium into a beautiful scenery . Specifications: Material: Resin Weight: 50 g Product size: Small Water Truck : 7*6.5*9cm Big Water Truck : 10*6.5*12cm Scope of application: aquarium, fish tank. Package includes: 1*Aquarium Windmill Notes: 1. Please allow 1-3cm error due to manual measurement. Thanks for your understanding. 2. Monitors are not calibrated same, item color displayed in photos may be showing slightly different from the real object. Please take the real one as standard.