By far, the almost PERFECT reef fish for a peaceful tank, with the exception of their tendency to carpet surf, they are a durable fish!

   Firefish are a long, slightly compressed fish with an eel-like body.  The face and the upper area of their head varies from a whitish yellow to yellow with iridescent white speckles.  Behind the mouth is a pearly white body, including the first dorsal fin, pelvic and pectoral fins which can have some yellow accents.  The long dorsal fin can have a red vertical pinstripe in front or a blue iridescent pinstripe with the balance of it being white.  Mid way down the length of the body, right at the beginning of the anal fin, the pearly white starts to blend into the orangish red color.  Both the anal and second dorsal fins follow the changing color of the body, with the very back of these fins and tail fin being a deep red to brick red color.  These fish grow to 3.5” (9 cm) and are mature at 2.5” (6.4 cm).  It is thought that they only live around 4 to 6 years in the wild and up to 10 years in captivity, similar to the Purple Firefish.  Without a lid, however, it will be much less than that.

   These fish belong to the family Microdesmidae, or Wormfishes. Before 1986, the Firefish were classified as blennies and gobies.  The Wormfish family comprise 10 genera with 73 species; however, dartfish are a sub-family that comprise 5 genera with 43 species, that include the closely related Purple Firefish, Nemateleotris decora and Helfrich’s Firefish, N. helfrichi.  They also lack a lateral line. Their elongated dorsal fin is used to signal other firefish as well as a “locking device” they use at night or if there is a predator trying to flush them out of their burrow or the rock work.  A very angry fish will flick it’s dorsal fish rapidly and quickly right before attacking other firefish

   These fish are great for beginners and adored by even the expert aquarist!  They are not picky about their surroundings or substrate, but they should have multiple places to hide quickly throughout the aquarium.  Firefish are easily startled, so having plenty of places will help them adjust.  While easy to keep, this depends on if there is a lid and appropriate tank mates.  The wrong tank mates can scare the Firefish into hiding, thus starving to death due to lack of feeding or being outcompeted by other fish.

   Only keep one per tank, unless they are a bonded male/female pair.  As docile as these fish seem, I have seen in person what they do to other Ffirefish, even in a 75 gallon tank.  It is almost a Dr. Jekyll and Mr. Hyde kind of thing so just don’t do it!  They may get along as small juveniles, but if they do not bond one will die.  They should not be kept with large, fast swimming wrasses that will scare them into hiding or even eat them!  Keep with peaceful fish and add flasher and fairy wrasses after them and choose small juvenile wrasses.  Avoid triggers, puffers, groupers, eels, large wrasses and other large fish that will eat this little guy.  Anthias are great because they are found at the upper levels and calmer clownfish and chromis are good tank mates. 

   Minimum tank size is 10 gallons if this is the only fish.  If other tank mates are desired, a tank that is at least 40 gallons is advisable.  Live rock should be mature and producing copepods by the time the Firefish is added.  Provide sand and an area of rubble that varies in size for them to burrow, as well as crevices and areas in the live rock for them to hide in when frightened or sleeping. They are found in waters that are quite warm so they can tolerate higher temperatures around 83˚F, or as low as 72˚F (22 – 28˚F).  One of their defenses is being able to swim incredibly fast so their ability to launch out of an open aquarium is inevitable.  A must is a tight fitting lid without any holes or crevices that you can fit your pinky tip into. 

Scientific Classification


Firefish – Quick Aquarium Care

Aquarist Experience Level:Intermediate
Aquarium Hardiness:Very Hardy
Minimum Tank Size:10 gal (38 L)
Size of fish – inches3.5 inches (8.89 cm)
Temperature:72.0 to 83.0° F (22.2 to 28.3&deg C)
Range ph:8.1-8.4
Diet Type:Omnivore

Habitat: Distribution / Background

The Firefish, Nemateleotris magnifica, was first described by Fowler in 1938.  They have many common names including:  Fire Dartfish, Firefish, Fire Goby, and Red Fire-Goby.  These dartfish are a sub-family of the wormfish family, having about 5 genera with 43 species.
   Firefish are found in the Indo-Pacific, from East Africa to the Hawaiian, Marquesans and Pitcairn Islands, then north to the Ryukyu Islands and south to New Caledonia and the Austral Islands which are the islands that are furthest south in Polynesia and throughout Micronesia.  They will inhabit upper parts of outer reef slopes, hovering over substrate.  They especially enjoy sandy rubble areas, where they can dart into crevices and holes when scared or grab food that the current brings them.  The deepest depth they have been found in is 230 feet (70 m), although they are typically found between 20 and 91 feet (6 – 28 m) in water that is 71.5˚F to 82.4˚F (22 – 28C).  They mainly feed on zooplankton as well as copepods and crustacean larvae. Firefish are solitary unless there is a male and female pair and juveniles are found in groups in the wild.  At night, several may share the same burrow.

   Firefish are on the IUCN Red List for Least Concerned.  The threats are Crown of Thorns Starfish invasions, water pollution, and population issues.  The issues such as bleaching, industrialization and over collection of the Firefish are reported in East African and Indonesian waters.  It is yet to be determined how their numbers are fairing.  In other localities, the population is strong where there are reefs that are in good condition.

Similar Species:

  • Purple Firefish (N. decora):  This fish is similar in size with a white to yellow body that can develop a deep purple in the back areas.  The fins are purple and red and they have a purple line forehead.  Their first dorsal fin is almost as short as their anal fin.
  • Helfrich’s Firefis (N. helfrichi):  This fish is all light purple with a yellow face, purple stripe on the head and a longer first dorsal fin similar to the Firefish
  • Scientific Name: Nemateleotris magnifica
  • Social Grouping: Varies – Juveniles-small groups. Adults are solitary or in mated pairs.
  • IUCN Red List: LC – Least Concern – Bleaching, Industrialization, over collection, pollution, and Crown of Thorns Starfish invasions.


   Firefish are a long, slender, eel-like fish that lacks a lateral line.  Their first dorsal fin has a long spine which is used to communicate with other Firefish which is followed by a much shorter spines and rays.  The second dorsal fin is also short and starts just above the area where the anal fin starts, with both extending back to the tail fin.  Their scales are tight fitting circles (cycloid scales) which helps them swim ridiculously fast.  The color starts with some yellow on the mouth and head, with tiny iridescent speckles.  The first part of the body is a pearly white, including the very long first dorsal fin which can have a little red or blue in the front part.  The pectoral fins are clear and the anal fins are white and can have some iridescence and/or yellow coloring.  Once this pearly white color meets the beginning of the anal fin and second dorsal fin, which is about 1/2 way down the body, it starts to morph into an orangish red.  At the very end, including the back edges of the second dorsal and anal fins and the tail fin the color turns even darker, more like a brick red.  The second dorsal fin and anal fin change color as the body color changes.  These fish grow to 3.5” (9 cm) and are mature at 2.5” (6.4 cm).  Similar to the Purple Firefish, they may live around 4 to 6 years in the wild due to predation, however with a tight fitting lid, they can live up to 10 years in captivity. 

  • Size of fish – inches: 3.5 inches (8.89 cm) – Firefish reach adulthood around 2.5” (6.4 cm)

  • Lifespan: 10 years – 4-6 years in the wild and up to 10 years in captivity. 

Fish Keeping Difficulty

   Their health is actually directly related to their tank mates.  Fast swimming larger fish will keep them in hiding, starving themselves to death out of fright.  Fish that are competitive for food can also limit the amount of food they get, however if attention is given to them, this can be overcome.  As long as their tank mates are peaceful, mellow swimmers and they cannot eat them, they will be fine.  They do best in a reef environment due to their need for copepods, zooplankton and other small foods found in such a tank.  They are quite durable little fish, however if they are sick, avoid meds with copper or other metals and organic dyes.  Fresh water dips that have matching pH and temperature must have netting covering them (submerged) because they will jump out.  Speaking of jumping out, yes they will jump out of any aquarium made by man.  Use a lid and be sure any equipment is tightly fitted to the black back strip or overflows are covered.  Even a small hole that you can fit your pinky into, it is a possible escape hatch for Firefish.

  • Aquarium Hardiness: Very Hardy
  • Aquarist Experience Level: Intermediate – As long as the beginner uses a lid with no holes and no aggressive tank mates.

Foods and Feeding

   Provide your carnivore Firefish with a mature tank that has live rock with live foods on it just in case they do not eat when first acquired.  Feed them mysis, minced scallops, shrimp, and other marine flesh from fresh or frozen/thawed sources.  Freeze dried mysis can be used to soak up vitamins, but may not be nutritious enough long term if that is the only food.  They can loose their color from lack of a varied diet.  These carnivores may accept flake or sinking pellets that are for carnivores, although it not common unless they learn it from other fish.  Live foods are best if they are not eating initially.  Gut load your live brine or mysis with Selcon or Vibrance soaked food before feeding.  While adults can be fed once per day, juveniles need to be fed 2 to 3 times per day.

  • Diet Type: Carnivore
  • Flake Food: Yes
  • Tablet / Pellet: Yes – Sinking
  • Live foods (fishes, shrimps, worms): Some of Diet – To get them to start feeding.

  • Meaty Food: All of Diet
  • Feeding Frequency: Several feedings per day – Juveniles should be fed 2 to 3 times daily.

Aquarium Care

Reef tanks

  • Nano/Small tanks up to 40 gallons, perform 5% water changes weekly.
  • Medium sized up to 90 gallons, perform 15% bi-weekly. 
  • Large Tanks 100 gallons and over, once water is aged and stable can be changed 10% bi-weekly to 20% monthly, depending on bioload.

Fish only tanks:

  • Nano/Small tanks up to 40 gallons, perform 15% water changes bi-weekly.
  • Medium sized up to 90 gallons, perform 20% to 30% monthly depending on bioload. 
  • Large Tanks 100 gallons and over, once water is aged and stable can be changed 20% to 30% every 6 weeks depending on bioload.

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: Weekly

Aquarium Setup

   Provide them with a tank that is at least 10 gallons.  They are fine in a nano, as long as they are the only fish and there is a lid.  If tank mates are desired, a 40 gallon would be appropriate, or larger depending on the needs of their tank mates. Two that are not mated pair in a 75 will end up in a fight, so providing a tank that is at least 6 feet for two may work out but there is no guarantee.  They need lots of places to hide when scared, so provide this with mature live rock.  At night they use their dorsal fin to wedge themselves into the rock work or their burrow while they sleep.  Water movement that flows towards them, at their favorite spot, is ideal.  Keep a tight lid on the aquarium.  A sandy substrate with various sizes of rubble provide burrowing material.  Lighting is fine, however when they are first acquired, keep them in a dimly lit tank, (quarantine) and you can slowly get them used to bright lighting over a few weeks.  They can tolerate temperatures between 72 and 83˚F (22 – 28˚C).   These fish need a lid no matter what the tank size or you WILL find them on the carpet/tile/wood floor surrounding your tank.  Even a small hole will be found for them to jump through.  When afraid they swim at incredible speeds (their defense in the wild) and their aim is incredible!  That being said, they will find their way into overflows or anything that is large enough for them to slip through.

  • Minimum Tank Size: 10 gal (38 L) – This would be only for the Firefish and no other fish.
  • Suitable for Nano Tank: Yes – As long as there is a lid
  • Live Rock Requirement: Typical Plus Hiding Places
  • Substrate Type: Mix – Sand + Coral – With various sizes of rubble
  • Lighting Needs: Low – subdued lighting – Keep in subdued lighting when first acquired.
  • Temperature: 72.0 to 83.0° F (22.2 to 28.3&deg C)
  • Breeding Temperature: – unknown
  • Specific gravity: 1.023-1.025 SG
  • Range ph: 8.1-8.4
  • Brackish: No
  • Water Movement: Any
  • Water Region: Middle – They typically hover about 12” off the bottom unless afraid then then stay close to the bottom

Social Behaviors

   Firefish male and female pairs get along great, staying side by side, however this is a hard combination to find.  Adding several juveniles to a large tank and seeing if any pair up is your best bet, but remove any others or they will be killed.  Firefish will seek out and destroy other Firefish, in all but the largest tanks that are at least 6 feet long.  Even then, there is no guarantee as some aquarists have experienced.

   When it comes to other dartfish, they don’t seem to be as aggressive, however, if you are adding another species in the tank, keep an eye out.  It will not take long to figure out if they are welcome.  Ideally, they should be added at the same time as juveniles.  Compatible fish are peaceful fish that are slow swimming and will not compete for food.  Firefish have been known to hide and starve to death if there are fast swimming or large fish in the tank.  Large wrasses will eat them and the more aggressive tangs are not good tank mates either.  It has been said to pass on tangs if you have one of these fish; however, if you have an older dartfish and then add a very small small tang, the dartfish may get used to it and not feel threatened.  They are all different, tolerating some fish and not others.  Clownfish, except for the aggressive species are fine, along with anthias which are found on the upper levels of the tank, and peaceful chromis, flasher wrasses and the fairy wrasses that are the mid to smaller species.  I have a Solar Fairy Wrasse (C. solorensis) that gets along fine with my Firefish, who is not in the least bothered by him.  The fairy wrasse was added as a juvenile once the Firefish was established.  Mellow butterfly fish and angelfish should be okay, just keep an eye on them.  If they hide for more than a few days, someone has to go!  Do not house with triggers, puffers, groupers, large wrasses, or any other fish that can eat this fish whole.  Avoid dottybacks which include pseudochromis, and avoid all but the most docile damsels.

   The Firefish is the ideal reef candidate.  They will not bother any corals in any way what so ever! 

   All inverts except some copepods are safe from the Firefish.

  • Venomous: No
  • Temperament: Peaceful
  • Compatible with:
    • Same species – conspecifics: Sometimes – Only bonded male/female pairs or small juveniles.

    • Peaceful fish (gobies, dartfish, assessors, fairy wrasses): Safe – Smaller juvenile fairy flasher wrasses added after Firefish is established
    • Semi-Aggressive (anthias, clownfish, dwarf angels): Monitor – No aggressive clownfish or aggressive dwarf angelfish.
    • Threat
    • Large Semi-Aggressive (tangs, large angels, large wrasses): Monitor – Adding a very mellow baby tang like a Kole Tang after your Firefish is full grown and established may be okay in a larger tank
    • Large Aggressive, Predatory (lionfish, groupers, soapfish): Threat
    • Monitor – Mandarins are fine, however they will compete for copepods with the Firefish.
    • Anemones: Safe
    • Mushroom Anemones – Corallimorphs: Safe
    • LPS corals: Safe
    • SPS corals: Safe
    • Gorgonians, Sea Fans: Safe
    • Leather Corals: Safe
    • Soft Corals (xenias, tree corals): Safe
    • Star Polyps, Organ Pipe Coral: Safe
    • Zoanthids – Button Polyps, Sea Mats: Safe
    • Sponges, Tunicates: Safe
    • Shrimps, Crabs, Snails: Safe
    • Starfish: Safe
    • Feather Dusters, Bristle Worms, Flatworms: Safe
    • Clams, Scallops, Oysters: Safe
    • Copepods, Amphipods, Mini Brittle Stars: Monitor – Some copepods will be eaten

Sexual differences

   Although there are no color or major size differences, females are slightly smaller and have a slightly thinner body. Of the many couples I have seen, it seems the female’s long dorsal fin curves back just a little more and is slightly shorter than the male’s long dorsal fin. 

Breeding / Reproduction

   Firefish will start their courtship which includes displays and posturing in open water before spawning.  At dusk will they spawn, with the female laying eggs on the substrate and then the male fertilizing them.  These little eggs are protected until they are ready to hatch.  Larvae are pelagic or free floating and will settle into the reef when they are large enough.

   They have spawned in captivity, so far no reports of successful breeding. 

  • Ease of Breeding: Unknown

Fish Diseases

   These fish are rather healthy, with their biggest issues being put in a tank with aggressive fish and then starving to death because they do not want to come out.  The other issue is carpet surfing, and they WILL if there is no lid or there is a lid that still has some small holes.  Egg crate will not work.  

   If they do fall ill, the typical treatments are okay with a few to keep away from.  These include medications that have metals in them like copper, etc.  Organic dyes can be too harsh for them as well.  If doing a fresh water dip, be warned that they WILL jump  out, so use a fine mesh to keep them submerged.


   These fish are everywhere all the time and they run from $15.00 to $25.00 USD for a 1.5” to 2” specimen.  (May, 2015)



Featured Image Credit: bluehand, Shutterstock