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Care guide · Marine fish

Firefish

Nemateleotris magnifica

Firefish — Nemateleotris magnifica
Photo: Jenny (JennyHuang) from Taipei · Source · CC BY 2.0Resized and compressed; no cropping or colour changes.

The firefish Nemateleotris magnifica often hovers just above a refuge, its elongated front dorsal fin held like a small flag. Its pale front half grades into a red-orange rear half. This slender reef fish catches small food particles from the water and particularly needs calm surroundings, an escape hole and a genuinely close-fitting cover. A small adult size does not make every small or heavily stocked tank suitable. Dominant neighbours can drive it into hiding until it eats too little. Keep one specimen as the cautious default, or choose a demonstrably compatible pair with specialist guidance. An arbitrary group can appear peaceful initially and develop problems later. The species belongs in a thoughtfully planned, quiet reef community, not as a test fish for a new system. At purchase, check that it is alert and actually feeds in the presence of other fish.

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At a glance

Adult size
Approximately 9 cm
Aquarium length
At least 80 cm
Minimum aquarium volume
At least 120 L
Temperature
24–26 °C
Specific gravity (SG at 25 °C)
1.024–1.026 SG
Salinity
32–35 ppt
pH
8.1–8.3
Difficulty
Moderate
Temperament
May jump, May jump
Diet
Filters small suspended food particles
Swimming zone
Middle
Reef safety
Generally reef safe
Suitable for beginners
Conditional
Social needs
Solitary
Keeping conspecifics
Only a confirmed compatible pair

Cautious husbandry guidance for adults, not a complete stocking calculation. Assess tank length, layout and the entire community together.

About this species

Allow for an adult length of approximately 9 cm. The elongated first dorsal spine and transition towards red fins help with identification. Other Nemateleotris species can appear under similar trade names, but their identity and origin must remain distinct in the care record. The slender build and relatively small mouth do not suit coarse food chunks. Sex and pair compatibility cannot reliably be established from a single sales photograph.

Natural habitat

The species inhabits tropical Indo-Pacific reefs, hovering over hard substrate close to an escape opening and intercepting particles carried by the current. In an aquarium it needs a calm feeding zone with sufficient water movement, without constantly struggling against a pump jet. A sheltered opening near the feeding site matters more than a broad exposed space without cover. Let the fish choose a secure base and avoid unnecessary changes after it settles.

Aquarium and layout

Allow approximately 120 L and 80 cm of length for a calm, lightly stocked setup. These are cautious planning thresholds, not a guarantee once extra residents are added. Provide narrow, safe openings in stable rockwork with free water nearby. Cover the entire tank, including cable passages and gaps beside pipes; a small gap can allow escape. Position pumps to retain quieter areas and avoid repeatedly driving the fish out of its only refuge during maintenance.

Water conditions

Prioritise stable conditions over large corrections aimed at an ideal number. Measure temperature, pH and salinity regularly and compare the aquarium with the water in which the fish was previously held. Appropriate acclimatisation depends on transport duration and water quality, so follow informed advice. Investigate detectable ammonia/ammonium. Nitrite and nitrate help track maturation and loading. Replace evaporation with suitable fresh water. A cover limits jumping but does not replace ventilation and well-oxygenated water movement.

Behaviour and group size

Darting into shelter when startled is normal; remaining permanently invisible is not a successful outcome. Watch whether dominant fish patrol its refuge and whether it dares to emerge at each feeding. Disturbance at night, sudden movement and aggression can trigger jumping, so a cover is necessary even in a seemingly peaceful tank. Extra cover may help when neighbours continually approach the escape hole, but persistent intimidation can require separation rather than further rearrangement.

Social behaviour and conspecifics

One specimen is a defensible choice in a normal mixed aquarium. A genuinely accepted pair is a possible exception. Two fish temporarily sharing a retailer’s tank are not necessarily a proven pair. Groups demand much more room and continuing observation; juveniles that tolerate each other may behave differently later. The planner therefore flags more than one individual. Persistent exclusion from food or shelter requires changing the combination, not simply increasing how much food enters the tank.

Feeding

Firefish are small plankton feeders favouring animal food. Fine mysis, enriched brine shrimp and suitable small marine foods can form a varied diet according to individual acceptance. Offer small portions in the water column near the familiar refuge. Slowly sinking food works only if the particles fit the mouth and faster neighbours do not intercept them first. Monitor abdominal condition and actual intake over several days. A “living” reef does not automatically provide enough food without deliberate feeding.

Reef safety

The species is generally kept as reef safe. Its normal feeding behaviour is not directed towards biting coral tissue. The main community problems usually involve fright, competition and predation by tankmates. A large stinging animal may itself threaten a small fish; the risk table primarily describes harm caused by the fish. A low rating in that direction must not be read as a complete guarantee of safety in both directions.

Stony corals

Generally low risk

Coral tissue feeding is not part of the documented normal feeding behaviour. Monitor contact and individual behaviour; low risk is not a guarantee.

Soft corals

Generally low risk

Coral tissue feeding is not part of the documented normal feeding behaviour. Monitor contact and individual behaviour; low risk is not a guarantee.

LPS corals

Generally low risk

Coral tissue feeding is not part of the documented normal feeding behaviour. Monitor contact and individual behaviour; low risk is not a guarantee.

SPS corals

Generally low risk

Coral tissue feeding is not part of the documented normal feeding behaviour. Monitor contact and individual behaviour; low risk is not a guarantee.

Anemones

Insufficient evidence

Insufficient species-specific evidence was found for this animal group. A general reef-safe label does not establish safety.

Keeping with other fish

Calm cardinalfish and a small peaceful goby often fit better than fast territorial hunters. An ocellaris or royal gramma may be possible if territories, refuges and feeding sites remain sufficiently separate. A six-line wrasse is more difficult because of its activity and potential intimidation. A Picasso triggerfish does not suit this vulnerable fish. Let shy residents establish their refuges first. Even a conditionally suitable pairing can fail in an overcrowded layout.

Keeping with invertebrates

Adult cleaner shrimp and common larger reef snails are not the usual prey type, whereas tiny free-swimming larvae and other plankton-like animals may be eaten. Distinguish ornamental adults from a breeding setup containing offspring. Large crabs and predatory shrimp can in turn threaten a resting firefish. Categories without enough species-specific evidence remain unknown. Adding an animal solely because the fish has a reef-safe label is not sufficient justification.

Large adult cleaner shrimp

Insufficient evidence

Insufficient species-specific evidence was found for this animal group. A general reef-safe label does not establish safety.

Small ornamental shrimp / juveniles

Insufficient evidence

Insufficient species-specific evidence was found for this animal group. A general reef-safe label does not establish safety.

Crabs

Insufficient evidence

Insufficient species-specific evidence was found for this animal group. A general reef-safe label does not establish safety.

Hermit crabs

Insufficient evidence

Insufficient species-specific evidence was found for this animal group. A general reef-safe label does not establish safety.

Snails

Insufficient evidence

Insufficient species-specific evidence was found for this animal group. A general reef-safe label does not establish safety.

Feather duster worms

Insufficient evidence

Insufficient species-specific evidence was found for this animal group. A general reef-safe label does not establish safety.

Clams / giant clams

Insufficient evidence

Insufficient species-specific evidence was found for this animal group. A general reef-safe label does not establish safety.

Starfish

Insufficient evidence

Insufficient species-specific evidence was found for this animal group. A general reef-safe label does not establish safety.

Sea urchins

Insufficient evidence

Insufficient species-specific evidence was found for this animal group. A general reef-safe label does not establish safety.

Small fish

Insufficient evidence

Insufficient species-specific evidence was found for this animal group. A general reef-safe label does not establish safety.

Breeding

Pairing and spawning are not an easy route to spontaneous breeding in a community aquarium. The consulted care sources do not support a broadly applicable home protocol with reliable timings and first foods, so no invented schedule or egg count is provided. Anyone intending to breed an established pair needs additional species-specific breeding information and separate rearing facilities. The first priority remains a peaceful arrangement in which both adults feed properly.

Possible problems

Weight loss despite food being offered often indicates inadequate intake, competition or another underlying problem. Check that this particular fish eats rather than merely watching food disappear. If it is missing, inspect the cover and overflow promptly, while remembering that some individuals stay in a cave for extended periods. Do not chase it out unnecessarily. Rapid breathing or abrupt behavioural changes call for water measurements and assessment of tankmates. Seek targeted help if the problem persists.

Sources & review

This care guide draws on several specialist sources and was last checked on .

View the sources