Lots of creatures live in coral reefs, including some tiny ones you might never have heard of. In this article, we will tell you about the importance of Foraminifera (also called forams), unicellular organisms with shells, that contribute to coral reefs in many ways. Just like corals, some forams living on the seafloor live closely together with microalgae. Some forams also thrive in similar environmental conditions (sunlight, temperature, salt) as corals. For this reason, forams can be used as reef “sensors”, to keep track of the overall health of coral reefs. They can even help to detect poor environmental conditions that might harm coral growth in the future. In this article, we will look at a study of an Indonesian reef ecosystem in which the foram communities living on the seafloor were monitored between 1997 and 2018.