In the video, a person is seen holding a sponge and cleaning the inside of a fish tank. The tank is filled with water, and there are several fish swimming around. The person is using the sponge to clean the sides of the tank, and the fish are swimming around the tank, occasionally coming close to the sponge. The person's movements are slow and deliberate, ensuring that they clean every inch of the tank. The fish are of various sizes and colors, and they seem to be enjoying the clean water. The tank is well-lit, and the water is clear, allowing for a good view of the fish and the cleaning process.