Clownfish

Clownfishes or anemonefishes are saltwater fishes found in the warm and tropical waters of the Indo-Pacific. They mainly inhabit coral reefs and have a distinctive colouration typically consisting of white vertical bars on a red, orange, yellow, brown or black background. Clownfishes developed a symbiotic and mutually beneficial relationship with sea anemones, on which they rely for shelter and protection from predators. In turn, clownfishes will protect the anemone from anemone-eating fish, as well as clean and fan them, and attract beneficial microorganisms with their waste.

https://en.wikipedia.org/wiki/Clownfish