Yellow watchman goby
Cryptocentrus cinctus
The yellow watchman goby lives close to the bottom and watches its surroundings from a secure opening. Cryptocentrus cinctus is known for its possible partnership with a suitable pistol shrimp, but an arbitrary shrimp does not automatically become a partner. It can also be kept without this association if its need for a sheltered bottom-oriented home is met. Yellow is familiar, although greyer forms occur too. This fish is neither an algae eater nor maintenance equipment: it needs appropriate animal food every day. A quiet tank with stable rocks, usable sand and food that reaches the bottom matters more than spectacularly strong flow. When buying, ask about captive-bred provenance and familiar foods. Beginners should consider it only after preparing both the layout and a workable feeding plan.
Plan your aquarium →At a glance
- Adult size
- Approximately 10 cm
- Aquarium length
- At least 80 cm
- Minimum aquarium volume
- At least 120 L
- Temperature
- 24–26 °C
- Specific gravity (SG at 25 °C)
- 1.024–1.026 SG
- Salinity
- 32–35 ppt
- pH
- 8.1–8.3
- Difficulty
- Moderate
- Temperament
- Forages on and in the substrate, May jump
- Diet
- Carnivore
- Swimming zone
- Bottom
- Reef safety
- Generally reef safe
- Suitable for beginners
- Conditional
- Social needs
- Solitary
- Keeping conspecifics
- Only a confirmed compatible pair, Territorial toward conspecifics
Cautious husbandry guidance for adults, not a complete stocking calculation. Assess tank length, layout and the entire community together.
About this species
The species can reach approximately 10 cm. A substantial head and pale spots help identify it, but yellow colour alone is unreliable. Other yellow gobies may differ in adult size, food and way of life, so check the scientific name. A photograph of two fish sharing an opening does not demonstrate general group suitability. Colour differences do not guarantee a pair either; actual mutual acceptance must be established.
Natural habitat
It occurs around sandy areas beside hard shelter on tropical Indo-Pacific reefs. An opening serves as its secure base, and the fish usually stays nearby. In a suitable symbiosis the goby watches while the shrimp works on the refuge. Reproduce this with movable sand beside a safely supported rock base. A bare glass bottom and a single decorative stone provide too little opportunity for normal use of the bottom zone.
Aquarium and layout
Use approximately 120 L and 80 cm of length as a cautious planning minimum. The area around the refuge matters more than additional water height. Provide usable sand and stable cavities, with rocks that do not depend on loose sand for support. Digging must not destabilise the structure. Fit a secure cover even though the fish normally stays low. Moderate flow and a feeding spot where food can settle prevent it immediately disappearing into a filter or behind rocks.
Water conditions
Stable temperature, pH and salinity are fundamental. Confirm biological maturity before introduction and measure nitrogen compounds when loading changes. Clean-looking sand does not prove good water quality. Remove leftovers selectively without repeatedly disturbing the entire substrate around the refuge. Match replacement seawater to the tank and top up evaporation with suitable fresh water. Do not add minerals simply because the fish may share a burrow with a shrimp; assess the shrimp’s needs separately.
Behaviour and group size
The goby may defend its immediate bottom territory, especially against conspecifics or fish seeking the same opening, while appearing calm elsewhere. Watch whether it confidently takes food or is pushed back by busier neighbours. A fish visible only during the darkest hours may be intimidated. Do not repeatedly rebuild its surroundings just to improve visibility. A refuge the animal accepts is more important than a position convenient for the observer.
Feeding
Offer suitably small animal foods such as appropriate mysis, enriched brine shrimp and accepted marine foods reaching the bottom. Check that the goby swallows rather than merely striking at oversized particles. A feeding pipette can deliver food nearby without driving it from shelter. Feed the fish deliberately even when it shares a burrow with a shrimp; the partnership guarantees no complete ration. A presumed cleaning role or incidental bottom life cannot replace controlled feeding.
Reef safety
The yellow watchman goby is generally regarded as reef safe. Coral tissue is not its normal feeding target. Its layout and possible digging partner may nevertheless affect loose stones and low objects. Do not place delicate colonies on foundations that can be undermined. Reef classification is not approval for every possible companion. Separate invertebrate assessments remain authoritative, including visible evidence gaps rather than unsupported assurances.
Keeping with other fish
Calm cardinalfish, an appropriate ocellaris and fish respecting the burrow entrance may be considered. A diamond goby also uses the bottom but feeds differently, so shared space and disturbance require extra assessment. An aggressive wrasse or large predator is not a suitable neighbour for a quietly waiting goby. Ensure faster fish do not intercept every portion. Read each relationship card alongside the actual floor area and refuges available to both species.
Keeping with invertebrates
A partnership with a suitable pistol shrimp requires species-specific selection and observation; not every pairing forms. Tiny ornamental shrimp or juveniles are a different situation and may be investigated as food. Large adult cleaner shrimp are assessed separately. Large crabs or predatory shrimp can also threaten the fish in the reverse direction. A favourable general reef label does not replace identifying the actual invertebrate, its adult size and the intended bottom layout.
Breeding
Commercial captive breeding is known. A suitable pair may reproduce at a sheltered spawning site, but subsequent development requires specialist rearing and appropriately small food. Do not turn a possible pair into an uncontrolled breeding experiment in an undersized community tank. This guide does not offer a sufficiently supported complete home protocol with fixed timings and food densities. Ask about the diet used for captive-bred stock and keep the initial feeding familiar. Healthy adult husbandry comes first.
Possible problems
Common problems include too little food reaching the bottom, gaps in the cover, undermined rockwork and intimidation. If the fish disappears, calmly inspect its normal opening, the overflow and the area around the tank. Weight loss calls for checking actual intake, not merely how much food is offered. Keep rocks and equipment secure around a digging partner. Measure water conditions after rapid breathing or changed behaviour and seek focused advice if problems persist. Repeated catching and rearrangement can increase stress.
Keeping with other species
Ocellaris clownfish
Suitable with conditionsThe bottom-dweller needs its own safe sandy area and targeted feeding. Keep rock foundations stable and prevent a territorial neighbour from blocking the refuge.
View species profile →
Royal gramma
Suitable with conditionsThe bottom-dweller needs its own safe sandy area and targeted feeding. Keep rock foundations stable and prevent a territorial neighbour from blocking the refuge.
View species profile →
Banggai cardinalfish
Suitable with conditionsThe bottom-dweller needs its own safe sandy area and targeted feeding. Keep rock foundations stable and prevent a territorial neighbour from blocking the refuge.
View species profile →
Pajama cardinalfish
Suitable with conditionsThe bottom-dweller needs its own safe sandy area and targeted feeding. Keep rock foundations stable and prevent a territorial neighbour from blocking the refuge.
View species profile →Sources & review
This care guide draws on several specialist sources and was last checked on .