Common Moray Eel

The Kidako Moray Eel is a rare beauty, whose juvenile patterns are similar to the snowflake eel!

The Kidako Moray Eel is dark brown with variety of shades of yellow, gold and tan that form big snowflake patterns!  Juveniles look similar to the smaller snowflake eel because of this.  Some look almost black when swimming in the wild under low light.  They have a continuous dorsal and anal fins and no boney gill plates over their elongated gill area.  They have very sharp teeth, and the teeth in the middle of their upper jaw are actually able to fold back against the roof of their mouth!  The Kidako Moray Eel reaches 39.4” (1+ m) and may live 10 to 30 years and are best kept by intermediate aquarists.  Many beginners do not realize the scope of the long term care and tank size needed to keep these eels as pets.

All morays, just by innocently breathing, can look very mean.  It’s now their fault, it’s the only way they know how to pull water down their throat and through their gills!  These guys are eaten in some places in Japan!  This is the meal that can bite back!  They have sharp teeth, and if they grab on to a bigger piece than they can swallow, the Kidako Moray Eel will break up larger prey items by rotating their body, tugging, knotting and thrashing, while smaller prey is eaten  whole.  They will manipulate fish so they swallow them head first.  Morays are commonly followed by other fish as they hunt.  These fish taking advantage of an easy meal that the Kidako Moray Eel flushes out of the reef.  On a side note, if you find your eel dried up on the floor, quickly put them back in the tank, since they shed their outer slime cover to protect themselves.  Be patient since it can take several hours to revive!

Kidako Moray Eels are easy to care for.  Offer a wide variety of foods like fresh squid flesh, marine fish flesh and crustacean flesh.  Do not over feed them, or they can develop a fatty liver or may barf up dinner.  Not something I would want to clean up!  Feed them until full, every 3 to 4 days, even if they beg to be fed more often.  Juveniles may need to be fed every other day, then less often as they age.  If they are not eating it is usually due to poor water quality, suppressed pH, overfeeding, or for no apparent reason.  Partial water changes or different foods may help.  It may take a few weeks for them to start feeding again.  Do not use decorations made of fiberglass, since it will cause sores on their scaleless bodies.  On that note, due to their lack of scales, do not use medications that have copper or organophosphates (masoten, dylox, Dipterex, Neguvon, and Malathion). 

It may be a bad idea to add fish mates.  If, however, you must have fish, they should be both too fast and too large to fit into their mouth.  The body of the fish should be several times deeper than the opening of the Kidako Moray Eel’s mouth. They have good eyesight and sharp teeth, so they are fish eaters and may see your hand as a yummy appetizer!  Feeding them with a feeding stick near their hideout is the best way to calm them so they won’t eat their fellow tank mates as soon, and this also lessens the risk of accidental bites.  They can learn to wait for food, which will helps prevent the feeding frenzy behavior that overturns rocks, displaces water and can end in a live fish being eaten instead.  Morays will not bother corals, but their movements can topple unsecured corals. Do not house with sharks, groupers or snappers, since these will eat eels.

Provide a tank that is at least 50 gallons per foot of eel, so 160 gallons for the Kidako Moray Eel would be a minimum size.   Older literature may state a smaller size, but their waste production demands a larger tank.  Also provide a very tight fitting and weighted down lid.  In this type of set up, if there isn’t a sump to oxygenate the water, use an air pump to provide the oxygen rich air space between the surface of the water and the lid. Without this application carbon dioxide will build up in that space and suppress the pH, leading to casualties!  As far as hideouts, they will occupy large PVC (3” around and 3 to 4 feet long), which you can surround with live rock.  They also will stay in any “cave” dwelling you offer, as long as it can hide their entire body.  Cable tie the rock work so their antics will not upset rock structures.  This is particularly important if they are in a reef setting.  Captive moray eels have been known to eat cleaner wrasse and cleaner shrimp.

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

Habitat: Distribution / Background

Kidako Moray Eel, Gymnothorax kidako, was first described by Temminck & Schlegel in 1846  The genus name Gymnothorax, while sounds like a body builder looking to get a six pack!  Let’s see if we can break that word down.  “Gymno” means naked in Greek, and “thorax” mean breast.   Yep, there’s a visual!  Now we are all picturing a guy at the gym, with no shirt on, standing in front of a mirror, flexing his thorax!   I wouldn’t call him an eel though…… The common names they are known by are Kidako’s Moray and Kikado Moray.   Nope I couldn’t find where the word Kidako comes from…. anyone?

Distribution – Habitat:
The Kidako Moray Eel is found in the Western Central Pacific from Japan, Taiwan, Ogasawara Islands, Hawaii and the Society Islands.  They live in deep crevices in shallow reefs from depths of  10 to 195 feet (3 to 6 m).  They eat squids, cuttlefish, and regular finned fish.  They are quite brave an will snatch fish being reeled in from divers!  Some areas of Japan eat them for food.

The Kidako Moray Eel is not yet evaluated on the IUCN Red List for Endangered Species.

• Scientific Name: Gymnothorax kidako
• Social Grouping: Solitary
• IUCN Red List: NE – Not Evaluated or not listed

Description

The Kidako Moray Eel is a long, deep bodied fish without pectoral or pelvic fins.  Their elongated gill openings have small holes, but do not have bony plate covers like other fish.  They have a continuous dorsal and anal fin, and no scales.  Their mouths have serious teeth, with the ones on the roof of the mouth being retractible, perfect for grabbing fish or inflicting a serious wound.  The coloring is brown with what looks like snowflake patterning all over the body in yellow, pale yellow or gold to tan coloring, depending on the specimen. They are found alone in the wild and reach a total of 39.4” (1+ m).  Moray eels can live from 10 to 30 years providing they don’t escape.

• Size of fish – inches: 39.4 inches (100.08 cm) – 39.4″ (1+ m)
• Lifespan: 10 years – Moray eels can live from 10 to 30 years providing they don’t escape.

Fish Keeping Difficulty

The Kidako Moray Eel is easy to care for, with the main challenges being tank size, tank mates and longevity of commitment.   They are a threat to any fish you may have in the tank.  To lessen, though not necessarily eliminate predation, feed your eel with a feeding stick in front of their hide out and they may learn to wait for food and not swim about trying to chow your other fish.  They need a place to completely hide their bodies such as a large 3” around or more PVC that is 3 to 4” long or similar structure.  Do not use fiberglass, since it irritates their skin.  If attempting more than one of these large eels, you may need a second job to pay for all that food and housing because you may need to put on an addition for that huge tank!  Seriously though, the tank should be double or 300 gallons, since they produce a lot of waste which deteriorates water quality.

• Aquarium Hardiness: Moderately hardy
• Aquarist Experience Level: Intermediate – Due to tank size, longevity and other factors above a beginners level.

Foods and Feeding

Kidako 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 – Adults, feed every 3 to 4 days.

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

Aquarium Setup

Provide a tank that is at least 160 gallons, which goes with the 50 gallons per foot rule of thumb for large eels.   Plenty of live rock, formed into hideouts or PVC arranged within the rock work is good.  As far as light is concerned, the area inside these hideouts should be completely dark. Temperature should be between 66 and 78˚F (19 to 26˚C) and pH should be 8.0 to 8.4.  Lower pH will result in your eel possibly 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.  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: 160 gal (606 L) – 160 gallons (606 liters) Older literature says 55 gallons, but figure on 50 gallons per foot 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
,
• Substrate Type: Sand – Sand would be better since they like to dig.
• Lighting Needs: Any – Ensure their hide out is completely dark inside
.
• Temperature: 66.0 to 78.0° F (18.9 to 25.6&deg C) – 66˚ F (19˚ C) Cooler water will result in the eel refusing to eat. 78˚ F (26˚ C)
• Breeding Temperature: – unknown
• Specific gravity: 1.023-1.025 SG
• Range ph: 8.0-8.4 – Low pH from too much organic waste will cause the eel to change in behavior and coloring.

• Brackish: No
• Water Movement: Strong – Provide decent water movement to help with filtration.
• Water Region: Bottom – Provide a weighted down, tight fitting lid.

Social Behaviors

Moray eels in general get along with their own and other species.  At most, there will be head shaking and an excessive opening of their jaws.  If another eel gets too close, at most they will put their mouth around the body of the offending eel, but rarely bite down.  If there is some locked jaw fighting, one will eventually give up and the torn flesh actually heels quickly.   If you are to house more than one, add the eels at the same time and make sure they are similar in size.  

Fish and smaller eels are always at risk for predation.  Use a feeding stick at the same time of day when feeding them in front of their hideout.  They have good vision so there is no need to whack them with it!  If they are kept well fed every 3 to 4 days, the other fish may be left alone, but there is no guarantee.

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 Kidako 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.

The only inverts these eels are a threat to are cuttlefish, shrimp and squid, if you happen to have those items!  Snails and starfish should be fine. 

• Venomous: No
• Temperament: Large Aggressive – Predatory
• Compatible with:
  • Same species – conspecifics: Sometimes
  • Peaceful fish (gobies, dartfish, assessors, fairy wrasses): Threat
  • Semi-Aggressive (anthias, clownfish, dwarf angels): Threat
  • Threat
  • Large Semi-Aggressive (tangs, large angels, large wrasses): Threat
  • Large Aggressive, Predatory (lionfish, groupers, soapfish): Threat
  • 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 – Snails are safe, but crabs and shrimp are not.
  • Starfish: Safe
  • Feather Dusters, Bristle Worms, Flatworms: Safe
  • Clams, Scallops, Oysters: Safe
  • Copepods, Amphipods, Mini Brittle Stars: Safe

Sex: Sexual differences

Unknown

Breeding / Reproduction

Little is known, 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.  A male and female pair of Kidako Moray Eels were observed spawning in the wild.  The male and female face each other with the front third of their bodies lifted off the substrate.  Then then quickly pushed their abdomens together and then separated just as quickly, releasing their gametes at the same time.  Moray eel eggs are 1.8 to 4 mm and the larvae are called leptocephalus.  They have small heads, large eyes and long, flattened, ribbon-like, clear bodies.
 

In very large systems, some have reported spawning, but without result. They are not currently bred in captivity.  See Breeding Marine Fish page for a description of how they reproduce in the wild.

• Ease of Breeding: Unknown

Fish Diseases

Occasionally, your Kidako Moray Eel will refuse to eat.  This can be caused by overfeeding, poor water conditions or a drop in water temperature.  Sometimes there seems to be no reason for an eel to go 2 weeks without eating, then it suddenly eats again.  If poor water conditions are suspected, it may take several weeks for them to start feeding again.  In the meantime, do several larger partial water changes to remedy the problem.  Morays have been known to go 2 months without eating, with no weight loss or 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

These eels are very rare and hard to find in the hobby.  When available they are very expensive.

References

Animal-World Refernces: Marine and Reef

Utsubo (Image Credit: Izuzuki, Wikimedia Commons CC BY-SA 3.0 Unported)