Cave fish were a kind of Rahi which dwelt in Ga-Metru. They defended themselves by absorbing liquid protodermis through their skin to inflate themselves and appear larger. Ga-Matoran later used dead cave fish to absorb leaks in protodermis purification vats. Cave fish were often seen in the waters around Mata Nui.1
Notes
Cave fish were a type of Rahi in Ga-Metru which defended themselves by absorbing liquid protodermis through their skin and using the fluid to inflate themselves and give the appearance of a larger creature.2