Firefish Goby

With a body that shades from a whitish-yellow head to orange-red toward the tail and a long, slender, upright dorsal fin, the firefish is one of the most elegant small fish for reef aquariums. It hovers a little above its burrow, picks off plankton brought by the current and, at the first sign of danger, darts instantly into its burrow or a rock crevice.

It is peaceful, reef safe and hardy. The real danger is jumping: when startled it leaps vertically and easily shoots out of an uncovered aquarium. So if you plan to keep a firefish, think about the lid first.

It lives on the outer reef slopes of the Indo-Pacific, over sand and rubble bottoms. It hovers alone or with its mate just above a burrow at the base of a rock or among rubble and does not stray from the burrow. Frequently flicking its upright dorsal fin helps it communicate with others of its kind.

• Volume: at least 75 liters for a single fish or a pair.
• Water: salinity 1.023–1.026 specific gravity, pH 8.1–8.4, temperature 24–27°C.
• Reef compatibility: reef safe; it does not touch corals, shrimp or snails.
• Lid: a fully closed or mesh lid is essential. Lights switching on and off suddenly and aggressive fish trigger jumping; turning the lights on gradually reduces the risk.
• Layout: porous rockwork and a sand substrate; crevices it can use as a burrow.

Carnivorous and a plankton feeder. Offer frozen mysis, brine shrimp, copepods and fine granules. It catches food in the water column as it drifts by; feeding small meals 2–3 times a day is best. If it is kept with fast, greedy fish, make sure it is not missing out on food.

Extremely peaceful and shy. It is easily bullied; kept with an aggressive fish, it hides constantly and wastes away. It is territorial toward unfamiliar members of its own species and other Nemateleotris species.

Good companions: clownfish, neon gobies, shrimp gobies, cardinalfish, royal gramma (in a large tank), blennies, cleaner shrimp.

Avoid: dottybacks, aggressive damsels, hawkfish, lionfish and large predators.

Kept singly or as a mated pair. Two unfamiliar adults together usually fight; the weaker one is chased and may be lost by jumping. Mated pairs constantly hover together and share the same burrow.

The pair lays its eggs inside the burrow and guards them. Breeding in the aquarium is rare; raising the planktonic larvae takes expertise.

• Jumping: the most common cause of loss.
• Marine ich and velvet: quarantine new arrivals.
• Shy individuals can miss meals and waste away; watch their feeding closely during the first weeks.

There is no reliable external difference.