Violet goby "Columnaris" and fin rot; which are bacterial infections that spread across the skin and fins of the fish. They are usually treated with antibacterial or antibiotic medications. Violet goby The violet goby ("Gobioides broussonnetii") is a species of goby native to marine, fresh and brackish waters near the Atlantic coast of North and South America from South Carolina in the United States of America, to northern Brazil. It prefers bays, estuaries and river mouths with muddy substrates. It is often marketed as the dragon goby or dragon fish. The Violet goby has a long, slender, eel-like body. Its dorsal and
Round goby Nord-Ostsee (Kiel) Canal. As of 2010, the westernmost site of round goby occurrence in Europe was the Lower River Scheldt, the tidal zone in the river mouth, and Albert Canal, Belgium. In 2011, the round goby began invading the fresh waters of France: the species appeared in the Rhine River (on the border between France and Germany), and in the French part of the Moselle River. In total, 52 parasite species are registered in the round goby in the native area. Most abundant parasites of the Black-Sea round goby are metacercariae of trematodes of Heterophyidae family, such as "Cryptocotyle concavum",