In the video, a person is seen pouring a bag of sand into a fish tank. The fish tank is already filled with water and has a layer of sand at the bottom. The person is holding the bag with both hands and pouring the sand in a steady stream, ensuring that it is evenly distributed throughout the tank. The sand is a light beige color and appears to be fine-grained. The fish tank is rectangular and has a clear glass front, allowing for a full view of the sand being poured. The person's hands are visible, but their face is not shown in the video.