A small, elegant marine dartfish with a pale body, magenta-purple face and fin highlights, and a flicking dorsal spine. Peaceful and reef-safe, it is an excellent, hardy beginner saltwater fish that needs a secure lid.
ℹ️
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Small; about 2.5-3.5 in (6-9 cm), with a tall first dorsal spine.
Lifespan
3–5 years
Social needs
solo
Native region
Indo-Pacific reefs, from East Africa and the Red Sea to the western Pacific
Origin
Old World
Climate
🌴 Tropical
Water type
🌊 Marine
Family
Microdesmidae
Genus
Nemateleotris
Part of the Dartfish
Small, peaceful, reef-safe marine fish (firefish and relatives) that hover above the substrate and dart into rockwork crevices when alarmed. Hardy and beginner-friendly, they are notorious jumpers and require a tightly covered aquarium.
From the minimum an animal needs to be kept humanely, up to the ideal setup. Bigger is almost always better — minimums are floors, not targets.
Photo coming soon
Minimum
Nano reef with lid
20 gal / 75 L nano reef
Nemateleotris decora is a shy jumper — TIGHT lid mandatory. Pairs (or single) in a nano reef with caves, peaceful tankmates, and gentle flow.
Photo coming soon
Recommended
Reef with bonded pair
30–55 gal / 110–200 L
Bonded pair in a peaceful reef. They hover above rock, retreating to caves when startled. Avoid aggressive fish — they will stress and starve.
Photo coming soon
Ideal
Mature mixed reef
75 gal+ / 280 L+ mixed reef
Larger reef with multiple bonded pairs of dartfish and firefish, abundant cover, and stable parameters. Full hovering display and dorsal flicks visible all day.
Life & growth stages
How this animal changes through its life — each stage often has its own care, diet and space needs.
Photo coming soon
Egg
Fish eggs are small, translucent spheres, often laid in clutches on plants, substrate, or in a nest — or carried/brooded by a parent in livebearing and mouth-brooding species. A dark eye spot and the curled embryo become visible inside as development progresses.
Photo coming soon
Fry
Newly hatched fry are tiny and semi-transparent, frequently still carrying a yolk sac that fuels them before they feed freely. They lack full fin structure and adult coloration, staying near cover until they can swim and forage on their own.
Photo coming soon
Juvenile
Juveniles look like miniature adults but with developing fins and muted or different markings; many species shift pattern and color as they mature. Growth is rapid at this stage given clean water and steady feeding.
Adult
Adults show the species' full size, finnage, and mature coloration, and are sexually mature. Many fish develop sex-specific differences in size, color, or fin shape, which can intensify during breeding.
Habitat & enclosure
Keep in a marine reef or fish-only tank of at least 20-30 gallons (75-110 L) with plenty of live rock providing caves and crevices for retreat. Maintain reef parameters: temperature 72-78F (22-26C), salinity 1.023-1.025 specific gravity, pH 8.1-8.4, and stable, low nutrient water. A tight-fitting lid is essential, as firefish are notorious jumpers that bolt for cover when startled. Provide a hovering open space above the rockwork.
Substrate
Use a marine aragonite sand bed, which buffers pH and suits reef tanks and many tankmates. The critical habitat element is live rock with holes and crevices for retreat rather than the substrate itself, since firefish hover and shelter in rockwork.
Equipment & setup
Run a protein skimmer and good biological filtration for low nutrients, a heater for the mid-70s F, and a powerhead for moderate reef flow. A secure, gap-free lid or mesh top is the single most important piece of equipment to prevent jumping. Reef lighting is for corals and rock; the fish itself has no special light needs.
Diet
A planktivorous carnivore. Feed small meaty marine foods several times a day in modest amounts: frozen mysis and brine shrimp, finely chopped seafood, copepods, and a quality marine pellet or flake. They feed in the water column on drifting food. Frequent small feedings keep this small fish well conditioned, as it has a fast metabolism.
Behavior & temperament
Peaceful, shy, and reef-safe, hovering above the rocks and darting into a hole when alarmed while flicking its tall dorsal fin. It will not harm corals or invertebrates. It is best kept singly or as a confirmed mated pair, since two unpaired firefish often fight; many other tankmates are fine as long as they are not aggressive. Excellent for nano and community reefs with calm fish.
Health
Hardy and disease-resistant when given stable water and adequate food, though prone to wasting if outcompeted by faster tankmates, so ensure it eats. The leading cause of loss is jumping out of an open or poorly sealed tank. Watch for marine ich (Cryptocaryon) and velvet; quarantine new arrivals. Provide enough hiding places so it feels secure and shows itself more.
Tips, DIY & hacks
Always cover the tank, including small gaps around equipment, to stop this jumper from escaping. To keep a pair, add both at once and ideally as a known mated pair; otherwise keep just one. Provide ample rockwork hideouts so it settles in and displays its color and dorsal flicking. Do not house it with aggressive or much larger fish that will bully it away from food.
