One of the first signs of a sick coral reef is seaweed creeping across the corals, stealing their precious sunny real estate. Healthy corals, however, aren't completely hopeless: in some reefs, small fishes, such as this broad-barred goby (Gobiodon histrio), help eat the seaweeds away. But how do corals contact the fish to ask for cleaning services? By sending out a chemical signal.
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Coral Goby Cleans Coral
![In some reefs, small fishes such as this broad-barred goby protect corals by eating invading seaweeds.](/sites/default/files/styles/3_2_large/public/2023-11/coral-goby.jpg.webp?itok=MgP6Pphw)