Yellowhead Moray Eel

The Fimbriated Moray Eel is a beautiful creature, sought after by aquarists for their interesting and varied patterns.  However, they tend to be very cryptic and need large systems.

The Fimbriated Moray Eel is pale tan to grayish brown overall.  Adults have irregularly spaced and differently sized spots and bars that are brown to black throughout the body.  The face area has sporadic spotting of different sizes on the head area.  Adults may have a pale yellow hue to the head, but the juveniles have an obviously yellow head, brown snout and their spots are larger, and the bars are not formed just yet.  Eels have only a dorsal and anal fin, which is continuous along the top and bottom of the fish.  They have very sharp teeth and keen eyesight.  The Fimbriated Moray Eel have 128 to 142 vertebrae, which sounds like a chiropractor’s dream, or nightmare, come true!  They are more geared toward intermediate aquarists due to their needs and long term care.

Fimbriated Moray Eels are very cryptic, which puts them low on the list of desirable aquatic pets.  They come out to eat, but hide again when they are full.  Even in the wild, very small juveniles are rarely seen.  Fimbriated Moray Eels have very sharp teeth and have been known to take down a fish that is 20% of their body length!  If they can’t orient the fish to go down their throat “head first,” they will knot, tug, thrash and spin their bodies to break it up into smaller pieces.  As eels hunt, they are followed by several different predatorial fish that take advantage of the Fimbriated Moray’s failed attempt to catch a meal!  That unwary fish may be temporarily relieved to have escaped the sharp jaws of the eel, only to be swallowed whole by his companion grouper, lion fish or goatfish!  This eel prefers to hunt at night.  The interesting way that eels breathe make them appear quite fierce.  They open their mouth to “inhale” water and then close their mouths to force the water down and over their gills.

Fimbriated Moray Eels are relatively hardy when housed correctly.  You may need to use live feeder shrimp and fish to get them eating initially, but they will take to “food on a stick” in a short period time.  A few things to keep in mind are: if you overfeed them, they puke; if the water is too cold, pH is too low, or water quality is bad, they won’t eat, and sometimes they just decide they don’t want to eat for 2 weeks.  Feed your juvenile eel every other day and as they get older, feed less often.  Because of their scaleless bodies, avoid fiberglass decorations and medicines that contain organophosphates or copper.  They produce copious amounts of body slime which helps prevent them from contracting most illness and parasites; however, it can tax water quality.

These large, reclusive eels are best kept without fish tank mates.  If you still want to attempt it, there are a few things to keep in mind.  Eels will eat any fish that is up to 20% of their length.  So a full grown 31.5” eel can eat even a deep bodied fish that is roughly under 7.”   Your fish should be over 7” and at least twice the depth of the eel’s gaping mouth.  The fish should also be fast enough to evade them and clever enough to hide out of their reach at night.  A large angelfish or large lion fish that is full grown will be safer than a slender, though longer wrasse!  If keeping another moray eel, the tank should be double the size to handle the waste.  A cleaner shrimp that has been in the tank first is less likely to be eaten than one added after the Fimbriated Moray Eel.  Cleaner Wrasses and Neon Gobies tend to be eaten in captivity.

Unlike older literature stating that the minimum tank size is 55 gallons, experience has taught aquarists that this is truly too small for quality of life.  A good rule of thumb is 50 gallons per foot or 12” of eel.  This will help keep water quality up and give the eel needed room to swim.   You may not SEE them swim, but if they come out at night, they need to stretch their legs….. oh, yeah, fins!   For the Fimbriated Moray Eel, plan on having a tank that is 125 gallons or more, but at least 24” in depth or more.  That is based roughly on a 31.5” eel.  It actually comes to 130 gallons, but there is no such tank size, unless it is custom made!  Provide a tight lid with no holes large enough for them to escape out of, and weigh the lid down.  Tanks that are shallower provide the eel with more leverage to push against the lid.  Cable tie rocks together so they do not fall on the eel and provide a hide out that is completely dark inside.  PVC does the trick!  If the tank does not have an overflow or sump, use an air pump to pump air into the space between the water surface and a solid lid.

For more Information on keeping this fish see:
Guide to a Happy, Healthy Marine Aquarium

Habitat: Distribution / Background

The Fimbriated Moray Eel, Gymnothorax fimbriatus, was first described by Bennett in 1831.  The common names they are known for describe their pattern or species name, and they are  the Darkspotted Moray, Yellowhead Moray Eel, Fimbriated Moray, Moray Eel, Spot-Face Moray, and Fimbriated Moray Eel.   The name Yellowhead Moray is descriptive of the juvenile to subadult coloring of the head. The genus name, Gymnothorax means “naked breast” in Greek, which to me, brings to mind a muscle bound guy at the gym with no shirt on, flexing in the mirror!  For our eel, however, this probably refers to the lack of scales, since they do not qualify for gym membership!

The Fimbriated Moray Eel is found in the Indo-Pacific from Madagascar to the Society Islands and then to the southern Japan and then south to Queensland, Australia and all of Micronesia.  They are found in protected inshore waters, such as harbors, bays, gulfs or even river basins, hiding within dead corals or caves.  They can also be found on patch reefs, on steep sandy slopes or in large sponges.  Juveniles are very cryptic and are rarely seen.  Adults have been known to share hiding places with White-eye Morays (Siderea thyrsoidea), but they are generally solitary creatures.  The Fimbriated Moray Eel is found from depths of 23 to 163 feet (7 to 50 m) and they eat fish, including parrotfish, as well as crabs and shrimp, and prefers to hunt at night.

They have not yet been evaluated by the IUCN Red List for Endangered Species.

• Scientific Name: Gymnothorax fimbriatus
• Social Grouping: Varies – They are generally solitary in the wild, but a pair can be kept in a very large 250 gallon or more tank.
• IUCN Red List: NE – Not Evaluated or not listed

Description

The Fimbriated Moray Eel is a long, deep-bodied, scaleless fish with a continuous dorsal and anal fin.  Adults are pale tan or grayish brown and can have 128 to 142 vertebrae!  The adult’s heads can have a very pale yellow hue to it and they all have irregularly sized bars and spots that are brown to black on their bodies.  The head has irregularly sized and scattered spots.  Juveniles have a lighter body color, but they can have a brown snout and a more intense yellow head, with larger evenly scattered black spots and unformed bars on the body.  As the eel ages, the brown and yellow fades, and the larger spots on the body start to join and form vertical bars.  The Fimbriated Moray Eel has keen eyesight and narrow jaws, with the lower one being slightly curved.  There is a single row of teeth in the front part of the jaws, with the back canines of the upper jaw alternating with small pointed teeth, and the back of the lower jaw has two pairs of long canines.  In the wild, they have been known to reach up to 31.5” (80 cm).  Moray eels are known to live from 10 to 30 or more years, providing they do not escape!  To date, the current age of a captive Fimbriated Moray Eel is 18 years old, over 39” and weighs about 10 pounds.

• Size of fish – inches: 31.5 inches (80.01 cm) – 31.5″ (80 cm) There is a Fimbriated Moray Eel in captivity that is 100 cm long and 10 pounds.
• Lifespan: 18 years – They can live 10 to 30 years. Currently there is one in captivity that is 18 years old.

Fish Keeping Difficulty

The Fimbriated Moray Eels are easy to care for, like most morays.  The challenges in keeping them, due to tank size, long life span and mates make them better suited for more experienced aquarists.  Feed them a wide variety of marine fish, shrimp and crustacean flesh that you can obtain from the grocery store.  Only feed them feeder shrimp or feeder fish like mollies to elicit a feeding response, until they can be switched over to other foods.  Poor water quality will cause them to stop eating.  They need a large PVC or cave that is dark inside to hide in and feel secure.  Do not use fiberglass products or medications with copper or organophosphates due to their scaleless bodies.  If attempting to keep more than one moray eel, tank should be at least 250 gallons or more to handle their waste and copious mucous production.  A good idea is to wait one day after you fed your eel to do a water change.

• Aquarium Hardiness: Moderately hardy
• Aquarist Experience Level: Intermediate – Tank size, longevity, and tank mates make this eel more suitable for Intermediate aquarists.

Foods and Feeding

Moray eels are carnivores.  Do not feed them goldfish or other fresh water fish.  These items are low in nutritional value and will eventually cause illness.  Feed them fresh squid, marine fish flesh, scallops, shrimp, and other marine flesh.  Feed them every 3 to 4 days to satiation, but no more than that or they will develop a fatty liver, or will throw up an extra meal, making for a huge mess in the tank!  Juveniles should be fed more often, every other day and less often as they grow.

• Diet Type: Carnivore
• Flake Food: No – They need fresh and varied marine fish and crustacean flesh.
• Tablet / Pellet: No – They need fresh and varied marine fish and crustacean flesh.
• Live foods (fishes, shrimps, worms): Some of Diet – Live fish can used to elicit a feeding response in an eel who is not eating.
• Meaty Food: All of Diet
• Feeding Frequency: Daily – Feed every 3 to 4 days to satiety for adults, more often as juveniles.

Aquarium Care

Reef tanks

Large Tanks 100 gallons and over, once water is aged and stable can be changed 15% to 20% weekly, depending on bioload.

Fish only tanks:

Large Tanks 100 gallons and over, 10 to 20% weekly.

For more information on maintaining a saltwater aquarium see: Saltwater Aquarium Basics: Maintenance. A reef tank will require specialized filtration and lighting equipment. Learn more about reef keeping see: Mini Reef Aquarium Basics.

• Water Changes: Bi-weekly – Do water changes the day after feeding

Aquarium Setup

Provide a tank that is at least 125 gallons, which goes by the 50 gallons per foot or 12,” of eel rule of thumb for the Fimbriated Moray.  Provide plenty of live rock, formed into hideouts or PVC arranged within the rock work or even affix rocks onto the PVC to disguise it.  As far as light is concerned, any light is acceptable, as long as the area inside these hideouts are completely dark. Temperature should be between 74 and 82˚F (23to 28˚C) and pH should be 8.0 to 8.4.  Lower pH will result in your Fimbriated Moray Eel going on a hunger strike and a change in behavior and color.  Normal seawater salinity of 1.023 on average is best, since that will also help keep the pH up.  Provide strong water movements to help with filtration and an air pump to infuse the space between the top of the water and the lid with oxygen, preventing carbon dioxide build up which can wreak havoc in a saltwater tank!  A very tight fitting lid, secured with heavy weights or very strong clips are needed since these eels are very strong and can push lids open.  That being said, the deeper tanks, the less leverage they have to push!  Make sure any holes on the lid are small enough to prevent the eel from escaping.  Sand is the best substrate since they like to burrow.  Juveniles can be housed in smaller tanks, with an estimate of 50 gallons per 12” or 1 foot.

• Minimum Tank Size: 125 gal (473 L) – 125 gallons (473 liters), Older literature says 55 gallons, but figure on 50 gallons per 12” of eel.

• Suitable for Nano Tank: No
• Live Rock Requirement: Typical Plus Hiding Places – Caves and deep crevices large enough to hide their entire body. Do not use fiberglass products.
• Substrate Type: Sand – Sand would be better since they like to dig.
• Lighting Needs: Any – Ensure their hide out is completely dark inside.
• Temperature: 74.0 to 82.0° F (23.3 to 27.8&deg C) – 74˚ F (23˚ C) Cooler water will result in the eel refusing to eat. 82˚ F (28˚ C)
• Breeding Temperature: – unknown
• Specific gravity: 1.023-1.025 SG – This level helps keep the pH up.
• Range ph: 8.0-8.4 – Low pH will cause the eel to stop eating and can cause a change in behavior and coloring.
• Brackish: No
• Water Movement: Strong – To aid in filtration.
• Water Region: Bottom – There should be a tight fitting lid and an air pump to if lid is solid.

Social Behaviors

Although they are found alone in the wild, they have been seen with other morays, so housing them together is fine, as long as the tank is twice as large and there are several hiding places.  Add both eels at the same time.  If there is any aggression, including an eel wrapping his mouth around the body of the other eel, don’t freak out.  They rarely bite down, so the risk of one being bit in half is insignificant, but watching it is hair raising!  They will often shake their heads and open their jaws very wide to tell the other eel to “get lost, dude!”  If they lock jaws and tear flesh, it is for a short time, and the wound will heal very quickly!

Fish are on the menu.  Fish are not “friends” in their eyes!  If you want to try to add fish to the system, they should be fast swimmers, more than twice as deep as the eels mouth and over 7” long.  For example, a large angelfish would be much safer than a large wrasse who is narrow and swallowable!  Use a feeding stick to feed the eel in front of it’s hideout.  This can help them learn to wait for food so they are less likely to go hunting at night.  Feed them until they are full, since a full eel will not try to eat their fish friends.  Add the eel last to this set up.  

Corals are left alone, and the movements of the eel behind the rocks actually helps stir dead zones.  The only time a coral is at risk is if the eel knocks it over or dislodges the rock the coral is affixed to.  This can easily be remedied by securing the rock and the coral.  SPS corals need much cleaner water than soft corals and some LPS.  Due to this fact, a Fimbriated Moray Eel may not be the best choice in such a reef set up, unless the reef is hundreds of gallons and can handle the waste these fish produce.

If a cleaner shrimp is desired, it should be in the tank before the eel is added, reducing, yet not eliminating the risk of predation.  These eels will eat crustaceans and other shrimp, however, large starfish should be left alone.

• Venomous: No
• Temperament: Large Aggressive – Predatory – Will eat fish that are not 2ce as deep as their mouth and up to 20% of the eel’s length.
• Compatible with:
  • Same species – conspecifics: Yes – Tank should be at least 250 gallons for 2 eels.

  • Peaceful fish (gobies, dartfish, assessors, fairy wrasses): Threat
  • Semi-Aggressive (anthias, clownfish, dwarf angels): Threat
  • Threat
  • Large Semi-Aggressive (tangs, large angels, large wrasses): Monitor – Fish should be over 20% more than the length of the eel or 7” or more and twice as deep as the eel’s mouth opening.
  • Large Aggressive, Predatory (lionfish, groupers, soapfish): Monitor – Fish should be over 20% more than the length of the eel or 7” or more and twice as deep as the eel’s mouth opening.
  • Threat
  • Anemones: Safe – Only if water quality is kept up and proper lighting is provided.
  • Mushroom Anemones – Corallimorphs: Safe – Only if water quality is kept up and proper lighting is provided.
  • LPS corals: Safe – Only if water quality is kept up and proper lighting is provided.
  • SPS corals: Safe – Only if water quality is kept up and proper lighting is provided.
  • Gorgonians, Sea Fans: Safe – Only if water quality is kept up and proper lighting is provided.
  • Leather Corals: Safe – Only if water quality is kept up and proper lighting is provided.
  • Soft Corals (xenias, tree corals): Safe – Only if water quality is kept up and proper lighting is provided.
  • Star Polyps, Organ Pipe Coral: Safe – Only if water quality is kept up and proper lighting is provided.
  • Zoanthids – Button Polyps, Sea Mats: Safe – Only if water quality is kept up and proper lighting is provided.
  • Sponges, Tunicates: Safe – Only if water quality is kept up and proper lighting is provided.
  • Shrimps, Crabs, Snails: Monitor – Adding cleaner shrimp first may prevent the eel from eating it.
  • Starfish: Safe
  • Feather Dusters, Bristle Worms, Flatworms: Safe
  • Clams, Scallops, Oysters: Safe
  • Copepods, Amphipods, Mini Brittle Stars: Safe

Sex: Sexual differences

Unknown

Breeding / Reproduction

There is not much information about the Fimbriated Moray Eel, although most morays are known to spawn in the spring and summer.  Some spawn several times during these seasons and some will spawn only once a year.  Some pairs of male and female morays have been observed in the wild, wrapped around each other with their mouths open.  They were pressing their abdomens together, then after they released their gametes into the water, they quickly pulled apart.  The eggs can number or 10,000 and they are 1.8 to 4 mm and the larvae are called leptochpalus.  The larvae have small heads, large eyes and long, flattened, ribbon-like, clear bodies..
 

See Breeding Marine Fish page for a description of how they reproduce in the wild.

• Ease of Breeding: Unknown

Fish Diseases

Occasionally, your Fimbriated Moray Eel will refuse to eat.  This can be caused by overfeeding, poor water conditions, the water water temperature drops too low, and sometimes there is no apparent reason for them to stop eating for 2 weeks, then it suddenly eats again.  If poor water conditions are suspected, it do several partial water changes to remedy water quality issues.  It still may take several weeks for them to start feeding again.  Don’t worry too much about them not eating right away, since morays have been known to go 2 months without eating, without weight loss or developing health issues. 

Rarely, eels are inflicted by parasites.  Their behavior of flicking their dorsal fin up and down, head-shaking or rubbing it’s head against rocks or other hard, rough surfaces is a dead giveaway.  Occasionally, eels contract nematode worms, which are squiggly, raised bumps under their skin.  Do not use medications containing copper compounds and oganophosphates, namely, masoten, dylox, Dipterex, Neguvon, and Malathion.  Malathion, for example is found in some medications to treat nematodes on fish.   What to do?  Massive water changes or place them in a treatment tank with PVC so they can hide, with an extremely heavy lid, and treat with erythromycin (Maracyn) for bacterial infections. 

Availability

Fimbriated Moray Eels are periodically seen online.  

References

Animal-World Refernces: Marine and Reef

Fimbriated Moray (Gymnothorax fimbriatus) (Image Credit: Bernard DUPONT, Wikimedia Commons CC BY-SA 2.0 Generic)