Yellow Watchman Goby
Cryptocentrus cinctus
Sand-sifting goby that shares a pistol-shrimp burrowBeginner
- Lifespan
- 4-6 years
- Size
- 8-10 cm (3-4 in)
- Social needs
- Singly or pair; pairs with a pistol shrimp
- Time
- Daily feeding; weekly testing/changes
- Cost
- Medium
- Diet
- Carnivore (mysis, brine, marine pellets)
Overview
What is this animal?
- The Yellow Watchman Goby is a stocky, bright-yellow (sometimes grey) goby known for its symbiotic partnership with pistol shrimp.
- The near-blind shrimp digs and maintains a burrow while the sharp-eyed goby stands guard, retreating into the shared den at any danger.
- It is hardy, peaceful, and reef-safe.
- Even without a shrimp it makes a charming bottom-dweller, perched on the sand watching the tank with its large eyes.
- Its burrowing and sand-sifting behaviour helps keep the substrate turned over and aerated.
Temperament
- Peaceful and reef-safe, the Yellow Watchman spends its time guarding its burrow and watching the tank.
- It is harmless to corals and most tankmates but may squabble with another bottom-dwelling goby over territory.
- Keep one per tank unless adding a bonded pair, and avoid housing it with larger predators or very aggressive fish.
- With its pistol-shrimp partner it shows interesting cooperative behaviour that makes it a standout reef resident.
A good fit for
- Beginners wanting interesting behaviour
- Sand-bedded reef tanks
- Keepers wanting the pistol-shrimp pairing
- Peaceful community stocking
Common mistakes to avoid
- No lid - they jump from the tank
- Shallow sand prevents natural burrowing
- Rock stacked on sand can collapse on burrows
- Aggressive tankmates outcompete it for food
Enclosure
Minimum 110 litres (29 US gallons)
Fine alone or with company. Singly or pair; pairs with a pistol shrimp
- Provide a cycled 110L (30 gal) tank with a deeper sand bed (5 cm+) for burrowing and live rock placed on the glass so digging cannot collapse it.
- Keep salinity 1.024-1.026, temperature 23-27°C (74-80°F), pH 8.1-8.4, and nitrate low.
- A secure lid is important because, like other gobies, they jump.
- Pair it with a single Tiger or Randall's pistol shrimp for the classic partnership.
- Stable water and a soft sand bed it can excavate keep this goby content and natural in behaviour.
Supplies
Setup
- Tank, stand and sump
- Return pump and powerheads
- Protein skimmer
- Reef lighting
- Rock and sand
- Salt mix, refractometer and test kits
- Quarantine tank
Ongoing
- Frozen mysis shrimp
- Frozen enriched brine shrimp
- Frozen cyclops
- Micro marine pellets
- Copepod bottle or refugium culture
- Turkey baster or pipette for target-feeding
- Small thawing cup and fine strainer
Safe substrate: Aragonite sand · Dry or cured live rock · Bare bottom
Care routine
Daily
- Check salinity, temperature and flow
- Check the lid and every gap
- Feed
- Head-count and look everyone over
- Top up evaporation with fresh water
Weekly
- Service the skimmer and filter socksevery 3 days
- Clean the glass
- Test the water
Monthly
- Water changeevery 2 weeks
- Calibrate the refractometer
- Check salt, RO/DI and reagents
- Replenish sand-bed life
Less often
- Deep-clean pumps and powerheadsevery 3 months
- Replace RO/DI filter mediaevery 6 months
Vet: Quarterly review with a lid check — every 3 months
Top resources for more info
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Diet
- The Yellow Watchman is a carnivore.
- Offer frozen mysis and brine shrimp, finely chopped seafood, and sinking marine pellets, fed once or twice daily.
- It will also sift the sand for tiny morsels and microfauna.
- Most individuals feed readily once settled, though shy ones eat more confidently with their pistol-shrimp partner present.
- Ensure food reaches the bottom, as this goby rarely chases food high in the water column and can be outcompeted by faster fish.
Health
- Watchman gobies are hardy and disease-resistant in stable water.
- The main risks are jumping from an open tank and stress from aggressive tankmates or unstable parameters, which can lead to ich or bacterial infection.
- Quarantine new fish, keep nitrate low, and provide secure burrows.
- Watch that it is getting enough food, since a thin, hollow-bellied goby signals it is being outcompeted.
- A calm, sand-bedded tank keeps it healthy for years.
Is your enclosure big enough?
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
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.
Bedding and substrate
In a marine system the rock and the sand are life support, and how you start them decides the first six months.
Safe
With a caveat
Never
This is our general list for saltwater fish. We have not built one specific to Gobies yet.
My kit says 0.25 ppm. Is that dangerous?
A liquid kit measures total ammonia, but only the un-ionised fraction is really toxic, and that fraction is governed by pH and temperature — each whole pH unit multiplies it roughly tenfold. So the same reading can be nearly harmless in one tank and lethal in another; this works out which one you are in.
Compare with other animals
The same axes for every animal, side by side — the way the guides are written makes that a fair comparison rather than two articles.
Gobies, side by side
Same axes, same care guides — the honest way to choose between types.
See all Gobies side by side →
