The Mandarin Dragonet is a strikingly coloured fish, swirled in green, orange, and blue.
Despite its calm, slow-moving charm, it is an advanced fish because of its specialised diet of small live invertebrates, mainly copepods.
Most mandarins die slowly of starvation in tanks that cannot sustain a copepod population.
Success needs a large, mature reef, ideally with a refugium, and patience to establish a thriving food supply.
Housing
Provide a well-established reef of at least 200L (55 gallons), and realistically larger, with abundant live rock and a sandbed that hosts copepods.
A refugium or pod-culturing system is strongly recommended to replenish the food supply.
Keep temperature 24-27C (75-81F), salinity 1.024-1.026, pH 8.1-8.4, and ammonia and nitrite at zero.
The tank must be biologically mature, never new, before a mandarin is introduced.
Diet
A specialised carnivore that grazes copepods and amphipods picked from rock and sand throughout the day.
A single fish can quickly exhaust a tank's pod population, so a refugium and regular pod top-ups are important.
Many individuals never accept prepared food, though some can be trained onto frozen cyclops, baby brine, or pellets, and captive-bred mandarins take prepared diets more readily.
Choose feeding specimens whenever possible.
Health
When properly fed, mandarins are reasonably hardy and resistant to ich thanks to a thick protective slime coat.
The main health risk is slow starvation, visible as a pinched belly and hollow stomach over weeks.
Quarantine and stable water remain important, but the single best safeguard is confirming the fish eats and maintaining a robust food supply.
A plump, rounded belly indicates a thriving mandarin.
Temperament
Peaceful, slow, and shy, it spends the day methodically hopping across rock and sand hunting pods.
It is reef-safe and harmless to corals and invertebrates, making a calm community fish.
Males are territorial toward other males, so keep only one male per tank; a male and female can coexist in a large system.
Avoid fast, greedy tankmates that outcompete it for food.
A good fit for
Experienced keepers with mature reefs
Tanks with a refugium and pod culture
Aquarists who choose captive-bred, feeding stock
Patient hobbyists with peaceful communities
Common mistakes to avoid
Starves without an established copepod supply
Sold for immature tanks that cannot feed it
Watch for a pinched, hollow belly
Greedy tankmates outcompete this slow feeder
Is your enclosure big enough?
Minimum volume200 litres (53 US gallons)
CompanyMust be housed alone. One male per tank; a female may be added
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.
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