In the video, a person's hand is seen holding a black cylindrical object, which is then placed into a fish tank. The fish tank is filled with water and has various plants and rocks inside. The person's hand is visible throughout the video, and the black cylindrical object is the main focus. The person's actions are deliberate and careful, ensuring that the object is placed securely in the tank. The fish tank appears to be well-maintained, with clear water and healthy-looking plants.