The video shows a group of fish swimming in an aquarium. The fish are of different sizes and colors, including yellow, green, and black. They are seen swimming around the tank, some near the bottom and others near the surface. The aquarium is filled with water and has a gravel-like substrate at the bottom. The fish are moving around freely, and there is no visible plant life or decorations in the tank. The lighting in the tank highlights the colors of the fish and the movement of the water.