The Diamond Watchman Goby is a pale, orange-spotted sand-sifter that constantly scoops mouthfuls of substrate to filter out food, keeping the sandbed clean and aerated.
It is attractive, peaceful, and endlessly busy.
It is rated intermediate because, like other sifting gobies, it depends on a mature sandbed rich in microfauna and can slowly starve in sterile tanks.
A deep sandbed and supplemental feeding are essential.
Housing
Provide a tank of at least 110L (30 gallons) with a deep, fine sandbed it can sift and burrow in, plus live rock for shelter.
A mature sandbed populated with micro-invertebrates supports its natural feeding.
Keep temperature 24-27C (75-81F), salinity 1.024-1.026, pH 8.1-8.4, and ammonia and nitrite at zero.
Its constant sifting can dust corals and shift aquascaping, so anchor rockwork securely.
Diet
A carnivore that sifts sand for copepods, worms, and other tiny invertebrates throughout the day.
As it depletes the sandbed's fauna, supplement with frozen mysis, brine shrimp, and sinking carnivore foods.
Many sifting gobies slowly waste away in tanks without enough sandbed life, so target-feeding and a deep, living sandbed are important.
A rounded belly confirms it is getting enough food.
Health
Reasonably hardy once feeding, but starvation in a depleted sandbed is the leading cause of decline.
Quarantine new fish, keep water stable, and confirm the goby is eating before relying on natural sifting.
Watch the belly profile and energy: a thin, listless fish needs more supplemental food.
It is also a jumper, so a secure lid prevents a common and avoidable loss.
Temperament
Peaceful and reef-safe, it ignores corals and other fish, spending its time sifting and excavating burrows under rocks.
It rarely bothers tankmates and is bullied only by very aggressive fish.
Keep singly or as a bonded male-female pair, as two unpaired individuals may quarrel.
Its burrowing can undermine rockwork, so build a stable aquascape on the bare bottom rather than on the sand.
A good fit for
Reef keepers wanting a clean sandbed
Tanks with a deep, mature sandbed
Keepers who will supplement feedings
Peaceful community and reef systems
Common mistakes to avoid
Starves in sterile or shallow sandbeds
Sifting dusts corals and shifts rockwork
Known jumper; needs a secure lid
Two unpaired gobies may fight
Is your enclosure big enough?
Minimum volume110 litres (29 US gallons)
CompanyFine alone or with company. Solitary or a bonded pair
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.
Beginner
Beginner
Beginner
Beginner
Intermediate
Intermediate