By Kirby Adams
As a youngster, I
recall being frightened horribly by a photograph of a Moray Eel in a picture
book about sea creatures. The monster was emerging, snake-like, from a rocky
reef with jaws agape and rows of sinister teeth glistening in its mouth. I
always tried to avoid looking at that page of the book. Twenty years
later, I found myself thawing whole squids to feed the six-foot-long Green Moray
(Gymnothorax funebris) that I was keeping in a 500 gallon aquarium.
Somewhere in between, Eels made a transformation from frightening to fascinating
in my mind. Today I consider the Moray Eels to be among the most rewarding
fish a marine aquarist can keep. Who would have thought?
Eels have charmed
me in many ways over the years. From the exceptional hardiness of some
species to the brilliant and exotic markings of others, the seduction was a
simple process once the fears of childhood were cast aside. As a
scientist, I’m fascinated by the history of Eels - the first Morays in the
fossil record show up about twenty million years ago in the Miocene period.
As a hobbyist, I’m simply enthralled with these primitive oddities of the sea.
The true Moray Eels
have been placed in the family Muraenidae, which comes from Muraena, the
Latin word for Eel. Many of the more well-known Morays belong to the genus
Gymnothorax, which is derived from the Greek gymno (naked) and
thorax (chest). This references the lack of pectoral fins on these
sleek-bodied fish. Below, I’ll present a few of my favorites from the
Gymnothorax genus and a couple of their cousins. First, we’ll look at
some basic Eel-keeping information.
When designing an
aquarium to house Moray Eels, consideration must be given to their well-deserved
reputation as escape artists. All Eels are Houdini-like in their ability
to escape from aquariums. If an opening in the cover is big enough for the
Eel to fit through, it is a safe bet the fish will be discovered on the floor
sooner or later. To prevent this, a tight-fitting lid that covers the
entire open area on top of the tank is essential. Any holes around filter
intakes or other equipment hanging on the rim of the aquarium must be plugged.
In an aquarium without a sump, this has the unfortunate effect of limiting
oxygen and gas exchange at the water surface. For these aquariums, an
excellent solution is the use of egg crate to cover all or part of the top of
the aquarium. This renders the tank escape-proof while still allowing
unimpeded light transmission and gas flow. Egg crate is used as a
fluorescent lamp diffuser and can be found in the lighting section of your
Diagrams of PVC placement for eel
habitat. Rock placed at a 45 degree angle (Top) within rock work,
and forming a tunnel (Bottom) that may or may not be viewable through
the front glass of the display.
Attention must also
be given to the aquascaping of the aquarium. Most Moray Eels are cave and
crevice dwellers, and will thus not appreciate a tank without adequate hiding
places. A reef tank with live rock stacked to create caves is sufficient
for many species of eel, particularly the smaller varieties. For larger
Eels, some engineering of specific caves may be necessary. PVC pipe makes
an excellent eel cave. Select pipe that is no more than 50% larger in
diameter than your Eel. To allow an Eel more freedom of choice and to
accommodate its growth, pipe of several different diameters can be used
throughout the tank. The pipe can be set pointing upwards at roughly a 45°
angle and the rockwork of the reef built around it. For added aesthetic
appeal, small rocks and rubble can be glued to the outside of the pipe using
silicone sealant or aquarium-safe glue. PVC can also be used to create a
cave in the substrate of a tank. A length of pipe can be laid horizontally
under the sand or crushed coral with a 45° elbow and a short length of pipe
emerging from the substrate. Rubble can be piled around the pipe where it
juts out, creating a very natural look which is made all the more striking by
the presence of the front end of an eel waving in the current! A display
done by my good friend Anthony Calfo utilized clear PVC for this underground
cave. The pipe was situated against the edge of the aquarium so the eel –
a beautiful Honeycomb Moray (Gymnothorax favagineus) in this case – could
be seen relaxing in his cave.
While they don’t
need an enormous amount of room for swimming, Eels are still big fish
appetites, so a large water volume is of great benefit. Very strong
biological filtration is a must and aggressive organic waste removal such as
provided by protein skimming is also a good idea. When in doubt, always
over-filter a tank with large predators.
further delay, let’s take a look at my five favorite Eels!
The snowflake moray (Echidna nebulosa)
is a great beginner's eel. They are relatively small and not very
The Snowflake Moray
is (no disrespect intended) the Comet Goldfish of the Moray Eels. Most
aquarists get their feet wet (pun definitely intended) in Eel collecting with
the purchase of a Snowflake. This popularity is well deserved, as
Echidna nebulosa is ideally suited to even a novice hobbyist with a
modestly-sized aquarium. Reaching a maximum size of less than 30 inches,
the Snowflake can be kept in tanks as small as 40 gallons. They are
primarily crustacean eaters and aren’t inclined to nip at larger tankmates.
Smaller fish however, should be considered at risk with a Snowflake Moray since
they are not completely devoted to a crustacean diet and are known to take fish
when the opportunity arises. It’s always fun to watch Eels preying on live
food, but the aquarist must avoid the temptation to train a Snowflake (or any
marine eel) to feed on freshwater feeder fish such as Goldfish, Guppies, or
Minnows. These are all lacking in nutrients essential to the Eel’s health,
can harbor diseases and harmful enzymes, and are generally not suitable foods
except in an emergency. Ghost Shrimp or common marine bait shrimp can be
used as treats, as can Fiddler Crabs or very small Crayfish. Again, many
of these lives foods will be deficient in fatty acids that are an essential part
of any marine fish’s diet, so they should be used only as the occasional treat.
The regular diet should consist of Silversides, uncooked shrimp, krill, pieces
of squid, or other marine meat of suitable size.
Zebra Morays can be finicky eaters,
but are among the safest to house with other fish.
Next, we’ll examine
my personal favorite, the Zebra Moray (Gymnomuraena zebra). Among
the many qualities of this animal is its finicky taste for crustaceans that
makes it one of the few large predatory fish that is almost completely save to
house with small fish. “Almost” is the key word in the preceding sentence,
as there are no absolutes in life or Eel-keeping, but I’ve never seen a Zebra
hunt and/or eat healthy fish in an aquarium. The only notable drawback to
Zebras is their tendency to be somewhat shy and occasionally unwilling to take
food. When first introduced to an aquarium it is often difficult to induce
a Zebra Moray to feed. When a newly introduced Eel refuses proper frozen
food, it may be necessary to train it on live food first. In the case of
Zebras, live crabs or Crayfish are a good choice for initial live food.
Crayfish are inexpensive and easy to obtain, but should only be used with
“problem” Eels that refuse to feed since their nutritional value for marine fish
is low. Once a Zebra is accepting live crayfish it is usually no problem
to get them to accept shrimp from a feeding stick. I have found uncooked,
shelled shrimp to be the best regular food for Zebra Morays.
The next two Eels
on the list are often confused with each other. These are the diminutive
Golden Moray of the Pacific and its larger cousin, the Golden Moray of the
Atlantic. Both are seen in the aquarium trade under the common name
“Golden Moray”. The Pacific Golden (Gymnothorax melatremus) is one
of the smallest of the true Moray Eels, reaching an adult length of less than
eight inches. The Atlantic Golden (Gymnothorax miliaris) is more
than 24 inches as an adult, but is still small enough to be a good candidate for
many home aquariums.
The more common and less expensive
"Golden Moray", G. miliaris from the Caribbean is a good aquarium
is somewhat reclusive and spends a lot of time hiding in crevices. In the
wild they will even occupy larger holes in sponges. In most cases, even
when hiding, the Eel’s head will be apparent protruding from the rocks. At
such a small size, this eel is only a threat to tiny fish and small crustaceans.
Coloration varies, but the most prized (and expensive!) specimens are a striking
golden yellow. These Eels are collected primarily from Hawaii. If
you want to make sure you’re ordering a G. melatremus and not a G.
miliaris, be certain that the fish is arriving from the Pacific Ocean!
is the more commonly encountered an much less expensive “Golden Moray” and also
makes a wonderful reef fish. Unlike many Gymnothorax, they are not
overly aggressive. Their natural habitat is sandy flats and rubble zones,
a condition easily replicated in an aquarium with some decent floor space.
Unfortunately, at two feet long, the Atlantic Golden Moray can’t be trusted with
small fish or most crustaceans. The best looking G. miliaris are collected
in the waters off the coast of Brazil. Again, keep in mind that if you are
getting a Golden Moray and it is coming from Brazil or the Caribbean, it will be
the bigger Golden, not the tiny Pacific variety.
The Green moray is seen far too often
in the aquarium trade. It is a very large, very aggressive fish
that require very large aquariums all to themselves and a knowledgeable
and brave keeper!
Finally, I complete
the discussion of my favorite Eels with a fish I must concede is terrible choice
for the vast majority of aquarists. This is the large and often fearsome
Green Moray (Gymnothorax funebris). Greens are common sights for
divers who frequent the waters of Florida and the Caribbean, but an unwary
hobbyist who hasn’t seen an adult in the wild might be tempted to purchase a
small Green Moray. Don’t be that unwary (and ill-informed) hobbyist!
Even a half grown
G. funebris can cause serious damage to an aquarist. An
adult can easily mutilate the hand that feeds it, or deliver a bite that leads
to severe infections and potentially the loss of a hand. They are
aggressive, bite without provocation, and eat any tankmates that are small
enough to be ripped apart. In short, they make extremely poor aquarium
subjects unless you are willing to devote a huge aquarium solely to one
specimen. I kept a 6.5 foot Green Moray in a 500 gallon aquarium, and I
consider that to be the smallest tank suitable for these eels. The tank
was fitted with a completely escape-proof locking lid. The Eel was fed
whole whitefish and squid from a fresh seafood market. Long feeding tongs
were obviously used, as hand-feeding a Green Moray is simply lunacy. Tank
maintenance and cleaning that required human hands and arms to enter the tank
was quite an adventure and only attempted when absolutely necessary. The
normal procedure involved a “spotter” who kept an eye on the eel and warned the
cleaner to quickly remove himself from the tank if the Eel showed any signs of
emerging from the rocks. Needless to say, this is not something any normal
aquarium hobbyist needs to get involved with. I thoroughly enjoyed my
experience with G. funebris and I have to admit that the site of the Eel
resting with its jaws open, allowing an Eel-cleaner shrimp to probe for tasty
debris amongst its razor-like teeth is one of the most stunning things I’ve
witnessed as an aquarist. Unfortunately I had to relocate the aquarium and
– fortunately – came to my senses and decided it was time for the moray to move
on to more suitable conditions. Even with my connections at various zoos
and aquariums, I found it nearly impossible to find someone willing to take a
huge Green Moray off my hands. Once again, I implore you not to follow in
my footsteps by purchasing this fish. If the Green Moray eel is also on
your list of favorite Eels, get to your local dive shop and book a trip to the
Cayman Islands to see one! [Editor's note: Being a
conscientious aquarist requires being prepared to take care of an animal for
it's entire life and at it's adult size! However, even in the case of an
honest mistake or changing circumstances, Zoos and Public Aquaria have strict
policies against accepting overgrown or no longer welcome animals, and releasing
them into the wild (especially in non-native habitat) is serious ecological
problem. Please plan well when keeping large animals!]
One final note
concerns a potential tank mate for Eels – the common cleaner shrimps mentioned
above. Lysmata amboinensis of the Pacific and its Atlantic look-alike
cousin, Lysmata grabhami have been dubbed “Eel cleaners” because of their
habit of climbing inside the gaping mouth of Eels and cleaning debris from
amongst the teeth. This behavior is not hard to observe in captivity,
provided your eels don’t eat your shrimp. The best method of avoiding this
is to introduce the shrimp first and then put the eel into the shrimp’s
environment. There is always the possibility the Eel will still consume
the shrimp, but in most cases the shrimp are recognized as being cleaners rather
than prey. Even the crustacean-eating Eels will usually allow a cleaner
shrimp to perform its service. Witnessing an Eel relaxing while a brightly
colored shrimp scavenges between its teeth is one of the many wonders of the
ocean an aquarist can have the pleasure of enjoying right at home.
The Conscientious Marine Aquarist. Microcosm Ltd. 1998.
Michael, Scott W.
Reef Fishes Vol. 1. Microcosm Ltd. 1998.
Moray Eels in the Aquarium. TFH Publications. 2005.