The video shows a yellow and purple fish swimming in an aquarium. The fish is moving around the tank, and there is a crab on the sandy bottom of the tank. The crab is moving its claws and appears to be interacting with the fish. The fish is swimming around the crab, and the crab is moving its claws in response. The tank appears to be well-lit, and the water is clear. The fish and the crab are the only two visible creatures in the tank.