The video shows a group of fish swimming in a tank. One of the fish is seen opening its mouth wide and then closing it, possibly indicating that it is trying to catch something or is in the process of feeding. The fish are of various sizes and colors, and the tank appears to be well-maintained with clear water. The fish are swimming around actively, and there is no visible plant life or decorations in the tank. The lighting is bright, and the tank seems to be indoors.