Moray eels belong to the family „Muraenidae“. There are approximately 200 species in 15 genera. They are found worldwide in tropical and temperate seas, particularly in relatively shallow water among reefs and rocks, as well as in estuarine areas. They vary considerably in size depending on species, from the ribbon moray at around 25 cm to the giant moray which can be as much as 4 metres in length. Their skin colors are as varied as the rainbow; you can see morays with skin that is speckled, striped, freckled or tattooed, and coloured in a variety of hues including brown, green, off white, yellow, black and blue. Most moray eel species differ from sea creatures as they have no side fins. They have a dorsal fin which runs almost the entire length of the body, from the head to the caudal and anal fins, and are made to appear like a snake by their absence of pectoral and pelvic fins. Moray eels secrete a mucus over their smooth skins in greater quantities than other eels, allowing them to swim fast around the reef without fear of abrasion. Due to the small size of the gills, morays have to continuously open and close their mouths in a gaping fashion to maintain a flow of water and facilitate respiration.
The Moray eel, characterized with a swaying serpent-head and teeth-filled jaw that continually opens and closes, is most commonly seen with only its head appearing from behind rocks. At night, however, this animal leaves its home along the reef to hunt. Morays are opportunistic omnivores, they are excellent predators, but do not make for very satisfying prey. Their diet consists mainly of other fish or cephalopods, as well as mollusks and crustaceans. Moray eels have poor vision and hearing senses, so they rely heavily on smell to locate prey. As described they go hunting mostly at night and their chief hunting tool is their excellent sense of smell which makes up for their poor eyesight. This means that weakened or dead creatures tend to be easy to detect and are therefore the moray eel's favoured food. It's quite rare to see moray eels swimming in open water during the day as they are nocturnal.
Moray eels are not suitable for reef tanks or tanks that house invertebrates or small fish.You must keep both their size and their predatory nature in mind when choosing their tank and tankmates. Large moray eels often prey on smaller eels. Also, moray eels sometimes escape from their aquarium and so you'll need a tight fitting lid. If you tend to maintain a moray please keep ever in mind moray eels have long life-spans. There are reports of moray eels living in captivity for almost 30 years.