Answer: seaweed smothers coral and herbivorous fish eat seaweed.
Explanation:
fish need the coral reefs because coral reefs are found in areas that support plant life in the ocean and since there's more than one type of plant life in the ocean seaweed has to grow somewhere so it grows where the coral grows like a battlefield for turf and if left alone the seaweed would smother the coral reef as well as absorb beneficial bacterias from the coral but because of certain types of herbivorous fish that eat seaweed this helps the coral survive and the seaweed from killing all the coral and the way that the coral helps the fish is the fish get seaweed to eat which is actually a good diet for herbivorous fish hence the word herbivorous
