Saltwater Fish

Firefish Goby

Nemateleotris magnifica

Slender dartfish with a flicking dorsal flag · Beginner

Lifespan: 3-5 years
Adult size: 7-8 cm (3 in)
Min. habitat: Aquarium 75L+ / 20gal+
Social needs: Singly or bonded pair; nervous in groups
Diet: Carnivore (mysis, brine, zooplankton, pellets)
Time: Daily feeding; weekly testing/changes
Cost: Medium

Overview

The Firefish is a slender dartfish, pale at the front fading to fiery orange-red at the tail, with a tall first dorsal fin it flicks like a flag.
Despite the common name it is a dartfish rather than a true goby.
Peaceful, reef-safe, and hardy, it is a good beginner fish.

It is timid and easily startled, hovering above the rockwork and darting into a burrow at any threat.
Given calm tankmates and secure hiding holes, it becomes a graceful, ever-present swimmer that adds movement to the mid-water zone.

Housing

A cycled 75L (20 gal) tank with rockwork providing several burrow-like crevices suits a single fish.
Keep salinity 1.024-1.026, temperature 23-26°C (74-79°F), pH 8.1-8.4, and nitrate low.
A tight, gap-free lid is essential because Firefish are accomplished jumpers.

Provide multiple crevices so it always has a refuge within reach, which helps it feel secure and stay visible.
House it only with peaceful tankmates, as boisterous fish keep a Firefish permanently hidden, stressed, and reluctant to feed.

Diet

The Firefish is a micro-carnivore that picks zooplankton from the water column.
Offer frozen mysis, brine shrimp, finely chopped seafood, and small marine pellets, fed once or twice daily in modest amounts.

Most accept prepared foods quickly once settled, though shy individuals feed better when tankmates are calm.
Small, frequent feedings suit its natural picking behaviour.
A varied diet maintains its tail colour and overall condition.

Health

Firefish are generally hardy but sensitive to stress and poor water quality.
The leading cause of death is jumping out of the tank, not disease, so a sealed lid is the single most important health measure.

They can develop marine ich or bacterial infections if stressed by aggressive tankmates or unstable conditions.
Quarantine new fish, keep nitrate low, and provide a calm environment.
A secure, peaceful tank lets a Firefish reach its full lifespan.

Temperament

Peaceful, shy, and reef-safe, the Firefish hovers above the rocks and dives for cover when startled.
It poses no threat to corals or invertebrates and is easily intimidated by pushier fish.

Keep one per tank or a known bonded pair, as two unbonded individuals usually fight.
It does best with equally gentle tankmates such as small gobies and cardinalfish, where it gains confidence and stays out in open water.

A good fit for

Beginners wanting graceful movement
Peaceful nano and community reefs
Reef-safe stocking plans
Keepers with a securely covered tank

Common mistakes to avoid

Any open gap in the lid - they jump out
Housing with aggressive tankmates
Keeping two unbonded individuals (fighting)
No burrows leaves them stressed and hidden

Is your enclosure big enough?

Minimum volume75 litres (20 US gallons)

CompanyFine alone or with company. Singly or bonded pair; nervous in groups

Check your own enclosure against this

Is this urgent?

In a reef, stability matters more than any single target number. A parameter moving fast does more damage than a parameter sitting slightly off.

Go now

Any detectable ammonia or nitriteWater change now with matched, mixed and aerated saltwater. Stop feeding. Directly toxic, and a marine system has less margin than a freshwater one.

Now

Temperature or salinity has moved sharplyCorrect slowly, over hours, not minutes. Check the heater and the top-off. The speed of the change does the damage. Correcting fast repeats the injury in the other direction.

Now

Rapid gilling, or a fish hanging in the flow breathing hardIncrease aeration and check temperature and salinity. Warm water holds less oxygen, and a heater failure shows up here first.

Now

Today

White spots, or a fine dusting like icing sugarIdentify which parasite before treating. Most reef tanks cannot be treated in place. The two common parasites look similar and need different handling; velvet can kill a tank in days.

Today

Corals closed for more than a day, or receding tissueTest alkalinity first, and compare it against the last reading rather than a target. Unstable alkalinity is the most commonly cited coral killer, and a swing shows up in the trend, never in a single point.

Today

A new fish added without quarantine now looks unwellRemove it to a separate system today if you can. Nearly every wipeout in a reef tank traces back to a skipped quarantine.

Today

Quarantine every new animal, including corals and inverts. It is the single practice that separates a reef that lasts from a reef that restarts.

This is general guidance for a healthy adult, not a diagnosis. An exotics vet who knows your animal always overrides it — and the time to find one is before you need one.

What it really costs

Setup, monthly, first year and across a whole life, itemised and with the electricity worked out from the actual wattage. Published figures for the same animal disagree by a factor of four, so the calculator shows ranges rather than picking one.

Work out the cost of a firefish goby

See all Gobies side by side →