Ask the WWM Crew
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How's that song go? "I'm in the mood for a moray? Unfortunately, with the a few exceptions, moray eels are best left in the seas from which they came. Almost all achieve too large a size, are too aggressive, even dangerous for aquarists, rendering bacteria-infested bites to the unwary. Some of the varieties that are frequently offered to the hobbyist refuse food or easily escape through the top of too-small, improperly covered aquariums.
But don't be totally turned off; there are a few gentle morays. Here I would like to encourage the keeping of the family's most adaptable species, the zebra moray, Gymnomuraena (formerly Echidna) zebra.
Systematics of The Moray Family:
Morays, family Muraenidae, are true eels (Order Anquilliformes). Muraenids lack scales, caudal, pelvic and pectoral fins; instead locomoting with long, continuous dorsal and anal fins. The local California green moray Gymnothorax mordax name reflects these traits; gymno thorax means "naked chest" in reference to morays' having no pectoral and pelvic fins and their (and all true eels) lack of scales. The specific name "mordax" is Greek for "biting". Don't be overly impressed or frightened by their open-mouthed appearance; morays are simply trying to ventilate through their small, restricted gill openings that lack covers; they're breathing!
There are about one hundred twenty species of morays in twelve genera, some dozen or so which are offered in the trade unseasonally. Muraenids are found worldwide in tropical to sub-tropical seas in tidepools to moderate depths. Though not often seen because of their secretive nature they make up a large part of the fish component on natural reefs.
Desirable Moray Traits:
"Good" morays and most other marine eel species are easy to pick out because there are so few of them. Particularly desirable are the morays of the genus Echidna, E. catenata E. pozyzona and E. nebulosa, the chain, girdled and snowflake morays respectively, and our highlighted species the zebra.
The Zebra is one of the smaller morays attaining two to three feet in overall length in captivity, and maybe four in the wild.
Compare this with the largest Muraenids at more than three meters; yes, close to ten feet. Many of the morays in the commonly offered genus Gymnothorax achieve a length of more than five feet. Trying to keep such large animals in small systems presents many difficulties; escape behavior, poor behavioral adjustment, and deteriorating water quality.
Though a multiple foot-long zebra is also a large animal, due to their more placid nature and lower metabolism they present a far slower and more stable "load" on your system.
Other moray species are opportunistic omnivores, trying to eat most all fishes and/or invertebrates; zebras are specialized crustacean feeders, lacking their cohorts sharp spike-like teeth.
Just the same, this species must be watched if/when your hands are in the tank, as it will bite. They have a great sense of olfaction, but unfortunately bad vision. Do not hand feed.
A marine system for a moray should be as large as possible. A minimum of forty gallons for the smallest of individuals. Tank shape should be more of a "standard" flat and wide than "show", hex, octagon or other novel tank shape.
After adjusting to a given set-up and routine of feeding, lighting and tankmates, a zebra moray will show itself more and more; however, these eels are reclusive in the wild and need a place to hide completely out of the light. A dark cave, PVC pipe, or rock/coral-covered pot is just the thing to grant yours a sense of security.
Morays are notorious "jumpers", exiting systems with even the most secure of tops. Zebras are better than all other species but may still squeeze out of a suitably large opening. Don't rely on a slightly lowered water level; keep a complete cover over the entire top of your system.
With zebras most all fishes are safe as long as they are more than mouth-size and your moray is regularly fed. These eels are too large and "clumsy" to be kept with most invertebrates, definitely not in reef set-ups, and will eventually eat any and all crustaceans.
Different species of morays are rarely found together in the wild, but I have mixed many types with the zebra with impunity. They seem to get along with most all other types of marine life (except shrimps, crabs...) with the usual proviso of watching for bullying triggers, puffers, other possible trouble-makers pestering them. Observe your charges carefully.
Echidnas and Gymnomuraena are invertebrate-eaters. Check their teeth; those crushing molars are for eating crabs and shrimps.
It is likely you will have to train your zebra onto frozen food. I strongly advise that marine aquarists try to keep their hands "out of the system" as much as possible, to prevent pollution, upsetting the livestock and injury. You can buy or build a "feeding stick, or rod" made from rigid plastic doweling or tubing to offer crustaceans near the front of your zebra.
How often should your moray be fed? The smaller ones maybe twice a week, the larger specimens once. Morays do not have to eat very often, and overfeeding them simply adds to water pollution and growth/size problems. I have never seen a specimen of Gymnomuraena starve to death. If yours doesn't feed for months and appears to be getting thin, offering a live shrimp will often spur it to feed.
Should be unnecessary if you select a healthy, clean specimen and provide a suitable habitat. I would recommend a simple freshwater dip for this species in lieu of the usual two to three week quarantine for new specimens. Avoid copper compounds, dye and organophosphate-containing remedies as these are deadly to true eels.
Odd behavior or markings on your specimens should prompt you to check water quality, possibly do a massive water change; not to automatically treat for an infectious or parasitic infection.
Zebras and other morays have celebrated wide parameter tolerance, 72-82 degrees F. for temperature, with specific gravity at 1.022 to 1.025. pH is a useful indicator for falling water quality; maintain your system in the high 7's to low 8.0's.
Due to being such large animals, providing a moray with copious amounts of food results in large, fluctuating metabolite loading and related degrading water quality. Therefore a protein skimmer and power filter is a must, in addition to good circulation, aeration, and biological filtration.
Frequent (at least monthly) twenty percent water changes are recommended, with concurrent gravel vacuuming and filter media cleaning/replacement.
Mount your heater(s) in a sump, otherwise out of the way where the moray won't hit it against the side or burn itself.
I've yet to see a "bad" specimen on import. Almost all adapt to captive care and eat within a week of arrival.
At a retailer's setting, look for signs of capture and transport abuse; torn fins, marks on the body, blood or other discoloration in the eyes. If in doubt as to purchase place a deposit, and wait a couple of weeks to take your zebra home.
Introducing a moray eel is little different than any other marine fish; perhaps with one exception, the degree to which it will hide on first being placed in the system.
I'd leave the lights off in the system but some on low in the room for a few days.
Should you have to move your zebra please consider my hard-won advice here. Though these fishes look 'tough as leather' they are not. Zebras and other morays are slippery and difficult to handle in standard fish nets; way too many end up on the floor.
Instead, collect yours up in a heavy-duty fish (or trash) bag with the sides rolled up by scooping it up after the rest of the livestock, decor and a good part of the system's water has been removed.
The Zebra Moray makes an excellent, albeit hidden show aquarium specimen for fish-only marine systems. This species easily adapts to aquarium conditions, readily accepting fresh or defrosted meaty foods. Unlike other morays, the zebra rarely bites tankmates or aquarists when doing routine maintenance. Once acclimated to a tank they prove long-lasting, disease resistant, and companionable specimens.
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Campbell, Douglas C.. 1980. Morays, the Ever Popular Eels. Freshwater and Marine Aquarium. 10/80.
Esterbauer, Hans. 1994. The Ecology & Behavior of Moray Eels. Tropical Fish Hobbyist. 2/94.
Fenner, Robert. 2000. The Zebra Moray Eel, Gymnomuraena zebra. FAMA 7/00.
Fenner, Robert. 1995. Moray eels of the family Muraenidae. TFH 3/95.
Gonzales, Deane. 1976. Puhi (Eel in Hawaiian). Marine Aquarist 7(7):76.
Margaritas, Anargyros. 1988. Sea Serpents in Your Home. Tropical Fish Hobbyist. 11/88.
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Schutt, Paul. 1976. Puhi (Hawaiian morays). Marine Aquarist 7(7):76.
Stratton, Richard F. 1997. The Zebra Moray. TFH 3/97.