Gymnothorax undulatus

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Facts
Latin name Gymnothorax undulatus - (Lacepède, 1803)
Local name Undulated moray
Family Muraenidae - Gymnothorax
Origin East Indian Ocean, West Indian Ocean, Australia, The Red Sea, Indonesia, East Pacific, Central/West Pacific
Max length 150 cm (59,1")
As aquarium fish
Minimum volume 1500 cm (396 gal)
Hardiness Hardy
Suitable for aquarium Suitable for special aquariums
Reef safe Reef safe with caution
Aggressiveness Aggressive towards similar species
Feed
Recommended Larger crustaceans (Shrimp, crabs...)
Fish
Beware of
Can bite

This species will at times bite people.

Threat towards crustaceans

This species poses a threat towards shrimps and crabs etc., which are relatively small.

Escape specialist

Morays can easily escape from aquaria, they can even move loose lids and glass covers without problems.

Threat to larger fish

This species can pose a threat towards fish that are relatively large in comparison to its own size. 

Aggressive

This species can be extremely aggressive towards other fish.

Be careful when keeping these fish together with peaceful or docile species. Regular feeding, plenty of hiding places and a lot of space can alleviate aggressive behavior to some degree.

Feeding of Moray eels

Morays should be fed a large meal every 3-4 days, as they otherwise can harm themselves by over eating.
If one has problems with getting the Morays to eat frozen fish or crustaceans, try moving the food in front of the fish with a tweezer. 

Do note, that the food must be varied and raw/fresh, whole shrimps or smelt (small fish) for example.

It can take a week before they start feeding in the aquarium, but this is not a problem.
Try feeding them live fish or shrimp if the Morays iare not eating frozen foods after a week. 

Keep in mind
Rearranges rocks and sand

This species has a habit of rearranging rocks and sand.

Make sure rocks are placed securely on the substrate, so they cannot toppled over.

Hiding places

This species needs good hiding places, for example, between live rocks.

Descriptions and further reading
Family description (Muraenidae)

Moray eels (Muraenidae) are predatory fish that will most commonly live off fish or crustaceans. 

To avoid overfeeding, the Moray must only be fed every 3-4 days, but may then also have a large meal.

They may dig up the substrate or move loose objects in the aquarium, so fastening the rocks and corals to the tank is a good idea.
Moray eels can easily escape from the tank if not tightly closed. They can lift lids and glass covers, do not underestimate their escape ability.

It is important that the Moray can, with its full length, hide between the rocks.

There are a few Moray eels which are suitable for reef aquaria, but the bigger species can only live in large tanks with other big fish.

Many Morays have a slightly poisonous bite, although it is not normally dangerous for people. One must not underestimate the strength of their bite however.  

FishBase
Aquarium trade Yes
Distribution Indo-Pacific: Red Sea and East Africa, including Walters Shoal (Ref. 33390) to French Polynesia, north to southern Japan and the Hawaiian Islands, south to the southern Great Barrier Reef. Eastern Central Pacific: Costa Rica and Panama (Ref. 9324).
English common names Undulated moray
Undulate moray
Undulated moray black barred garfish
Leopard moray
Danish common names Marmoreret muræne
German common names Leoparden-Muräne
French common names Murène ondulante
References and further reading

About references

Scott W. Michael. 2001. Reef Fishes volume 1 - TFH Publications / Microcosm Ltd. - (English)
Frank Marini. 2002. A Serpent For Your Reef Tank: A Look at Fish-Safe Eels - Reefkeeping Magazine - (English)
Mike Maddox. 2009. Morays! - Tropical Fish Hobbyist Magazine - (English)
Kirby Adams. Five Favorite Eels - Wet Web Media - (English)
Bob Fenner. The Moray Eels, Family Muraenidae, pt. 1 - Wet Web Media - (English)
Bob Fenner. The Moray Eels, Family Muraenidae, pt. 2, Less Aquarium Suitable Species - Wet Web Media - (English)
Marco Lichtenberger. 2007. Moray Eels Bite—But Are They Poisonous? - Tropical Fish Hobbyist - (English)