Common Names: undulated moray, undulate moray, mottled moray
Scientific Name: Gymnothorax undulatus (Lacepede, 1803)
From Where? The general Indo-Pacific area, from south-eastern Africa right up to southern Asia, then down along the Indonesian islands to the Great Barrier Reef. Is also found around Hawaii, the Red Sea and the eastern Pacific.
The younger eels are found in slightly shallower water along coasts, favouring crevices and lurking between rocks. Adults are found somewhat deeper, preferring to stay inconspicuous and remaining by a preferred lair.
Size: Adults are reported to reach a maximum length of 5 feet (1.5 meters). They aren't often kept in aquaria, so it is unknown if they assume a smaller maximum size in captivity. It'd be best to house them as if they'll reach 1.5 meters,
Foodstuffs: In the wild they'll hunt fish that are approximately their mouth size, as well as octopus and other smaller cephalopods. In your tank they might need to be weaned off live foods at first, but once you've conquered that problem they'll happily accept frozen fish, chopped squid, octopus tentacles and prawn pieces.
Hand feeding is NOT RECOMMENDED.
Water: Keep it within the 'typical' range of tropical marine conditions; an SG of about 1.020 to 1.026, pH between 8.0 and 8.3, and the temperature between 23°C and 26°C (74° and 78° F).
Aquarium Specifics: first and foremost, make sure you have a large tank on hand. G. undulatus is one of the largest morays around, and as such, need more space than most of the other morays you'll encounter. At a bare minimum, an adult will need a tank with a footprint of about 2 meters by 1 meter. The bigger the better.
These fish prefer to have a tank with lots and lots of hiding places, mainly in the form of rocks (live and artificial), pipes, and corals if you want. The substrate should be sandy for smaller specimens, as they like to sometimes dig under certain structures to create extra hiding places - on this note, make sure that all rock structures are secure. A young moray may undermine certain rocks while larger eels can knock-over piled up rock structures.
Try to keep the lighting toned down as this will help to make the fish more comfortable, and if you're lucky they'll eventually come out during the day.
Current isn't important but efficient filtration is - these carnivores produce a lot of waste from what they eat, and a good filter and even a protein skimmer are recommended. Water changes should also be frequent.
NB: as with pretty much any other eel, you need a good heavy lid and/or an equally good cover glass. They'll exploit even the smallest holes in the tank as escape routes, including those intended for wiring or filters.
Compatibility: As an out-and-out fish hunter, smaller fish are probably not the best tank mates for the Undulated Moray. Larger fish (excluding other morays, which will fight for hiding spaces) are fine though - bigger angels and butterflies normally do well. However, there are no promises with morays, so always keep an eye out if the moray is bothering or being bothered by anyone.
Almost completely suited to reef systems... the shrimps and smaller crustaceans are at some risk.
G. undulatus is almost completely incompatible with your hands. Beware when carrying out feeding or maintenance, as they have have sharp teeth and very bad eyesight - your hand will look just like food to them...
Specific Problems: large size, predator, escape artist, tank-polluter. One to carefully consider before adding to the tank.
Rarity: fairly rare. While they do have a decent range, they're not especially well known, and you may have to look for a specialist dealer who can help you.
Similar Species: Gymnothorax fimbriatus is often confused with this species (or vice versa). They have similar mouths I suppose. At times, shipments of G. fimbriatus may come in with a surprise of a G. undulatus as well.