In the video, a fish and a crab are seen in an aquarium. The fish is black and white with yellow fins and is swimming around the crab. The crab is brown and is crawling on the sandy bottom of the aquarium. The fish appears to be curious about the crab and is swimming around it, while the crab is moving slowly and appears to be aware of the fish's presence. The aquarium is well-lit, and the water is clear, allowing for a good view of the fish and crab.