There are two parasitic fish species on ON. One is the microscopic Ronmph, a creature which latches on to the outside of Giants and feed on their blood (similar to Lamprey). This relationship is symbiotic in all but the Gogh's case as the Ronmph actually clears the blood of foreign bodies in the process. The other parasitic fish species resembles a tapeworm and goes by the name of Yort. While it is difficult to see what a parasite such as this could bring to the proverbial table, it too clears foreign bodies from any ingested food, often leaving far more than enough for the Giant in question to thrive.