Ruki were small, aquatic fish Rahi. They were found in the waters around both Metru Nui and Mata Nui. On Mata Nui, they lived in Ga-Wahi. Although no threat individually, schools of Ruki were seen to drive off Tarakava and other much larger creatures. Their powerful jaws made them a consistent problem for Ga-Matoran, since they would chew through nets, dams, and any other objects they might find in the water.
Schools of Ruki minnows could be found in Gali's Bay. Ruki fish could be seen darting everywhere.
Ruki were small fish Rahi commonly found in the ocean around Metru Nui. Although they were not physically imposing, they had extremely powerful jaws, and schools of them were known to drive off Tarakava.