Wet Web Media explains that freshwater moray eels include the species Gymnothorax tile, Gymnothorax polyuranodon and Echidna rhodochilus. Gymnothorax tile eels are most common; they are gray with yellow spots and grow to 24 inches long. Other freshwater moray eels include the Indian mud moray, snowflake eel or gold-dust moray.
Although freshwater morays can survive in hard fresh water for up to two years, they need brackish or marine water to thrive. Their natural habitats are in coastal estuaries and mangrove swamps, and they are prone to disease when kept in fresh water. They often reject food when in fresh water or when subjected to other forms of stress.