Signigobius biocellatus (Twinspot Goby / Signal Goby / Crab-eye Goby)
• Small fish safe: ✅ Yes
• Small invert safe: ⚠ With caution (may consume very small ornamental shrimp)
• Coral safe: ✅ Yes
• Minimum tank size: 200L+ (preferably with a mature, deep sand bed)
• Adult size: ~10 cm (4 inches)
• Diet: Carnivorous (primarily feeds on small invertebrates within the sand; may accept live foods and, with acclimation, frozen or prepared foods)
• Be aware of: Requires a well-established aquarium with a deep, fine sand substrate for burrowing and feeding. Prone to starvation if adequate natural food sources are not available. May be territorial towards conspecifics unless kept as a mated pair. Prone to jumping, so a secure lid is essential.
Twinspot Goby (Signigobius biocellatus) – A Unique and Challenging Sand-Sifting Goby
The Twinspot Goby, also known as the Signal Goby or Crab-eye Goby, is a visually striking species renowned for its distinctive dorsal fin eyespots and intriguing behavior. While captivating, this goby presents specific care challenges, particularly concerning its dietary needs and habitat requirements. It is best suited for experienced aquarists prepared to meet its specialized care demands.
Appearance and Coloration
The Twinspot Goby is easily recognizable due to its:
• Two prominent eyespots on its dorsal fins, resembling crab eyes, which serve as a defense mechanism against predators.
• Tan to white body, adorned with orange to brown spots and a vertical orange stripe running through the eyes.
• Unique fin structure, with ventral and anal fins that resemble “four-wheel drive tires,” contributing to its nickname, the “4-Wheel Drive Goby.”
• A small, elongated shape, reaching up to 10 cm (4 inches) in length.
These markings and adaptations allow the Twinspot Goby to blend into its sandy surroundings, making it an interesting yet subtle addition to a reef tank.
Natural Habitat and Behaviour
Native to the Western Pacific, including regions such as Indonesia, the Philippines, and the Great Barrier Reef, the Twinspot Goby inhabits silty lagoons and sandy reef zones, where it:
• Constructs burrows in sandy substrates, often under coral rubble or debris.
• Sifts sand continuously, filtering out small invertebrates and organic matter, playing a crucial role in maintaining substrate health.
• Displays monogamous pairing, with both individuals participating in burrow maintenance and defense.
• Uses its dorsal fin spots to confuse predators, mimicking larger animals.
In captivity, replicating these natural conditions is essential for their well-being and longevity.
Tank Requirements and Water Parameters
Due to their specialized needs, Twinspot Gobies require a carefully planned aquarium environment:
• Minimum tank size: 200L+ (50 gallons) to provide adequate space and a stable environment.
• Substrate: A deep (at least 5 cm), fine sand bed to facilitate natural burrowing and feeding behaviors.
• Aquascape: Plenty of live rock and hiding spots, ensuring open sandy areas for sifting.
• Water parameters:
• Temperature: 22–27°C (72–81°F)
• pH: 8.1–8.4
• Salinity: 1.020–1.025
⚠ A well-established aquarium with a mature sand bed rich in microfauna is crucial to support their natural feeding habits.
Diet and Feeding
Twinspot Gobies are specialized feeders, primarily consuming small invertebrates within the sand. In captivity, meeting their dietary needs can be challenging:
• Natural feeding: They rely heavily on live microfauna present in a mature sand bed.
• Supplemental feeding: While some individuals may learn to accept:
• Live foods such as copepods and amphipods.
• Frozen mysis and brine shrimp, though they may not always recognize it as food.
• Finely chopped seafood such as shrimp and clam meat (offered near their burrow).
⚠ Due to their picky eating habits, they are prone to starvation in tanks lacking sufficient natural food sources. Regular monitoring of their body condition is essential.
Compatibility and Tank Mates
Twinspot Gobies are generally peaceful but have specific compatibility considerations:
✔ Other peaceful, non-aggressive fish that do not compete for the same food resources.
✔ Small reef fish, including Clownfish, Firefish, and Blennies.
✔ Reef-safe invertebrates, including snails and crabs.
Avoid housing with:
❌ Large, aggressive fish (e.g., Lionfish, large Wrasses, aggressive Dottybacks) that may harass or eat them.
❌ Fast-feeding fish, as Twinspot Gobies require slow, deliberate feeding.
❌ Other sand-sifting gobies, unless in a very large tank with separate territories.
⚠ If keeping a pair, ensure they are a bonded or mated pair to prevent territorial disputes.
Burrowing and Sand-Sifting Behavior
One of the biggest advantages of keeping a Twinspot Goby is its natural sand-cleaning activity:
• Constantly sifts through the sand, keeping it oxygenated and clean.
• Prevents detritus buildup, reducing harmful gas pockets.
• Creates burrows under rocks and coral rubble, which can sometimes shift the aquascape.
⚠ However, their constant digging can be a challenge if corals or live rock are placed too close to the substrate.
Health and Disease Considerations
Twinspot Gobies are delicate when first introduced but become hardy once established. However, they can be prone to:
• Malnutrition – The biggest risk, as they require constant access to live food sources.
• Marine Ich (Cryptocaryon irritans) – Often caused by stress or poor acclimation.
• Jumping incidents – A tight-fitting lid is essential to prevent losses.
To keep them healthy:
✔ Provide a well-established tank with a mature sand bed.
✔ Offer a varied diet with natural live food sources.
✔ Ensure stable water parameters with good filtration.
Lifespan and Long-Term Care
With proper care, Twinspot Gobies can live up to 3-5 years in captivity. Their fascinating burrowing behavior, sand-sifting benefits, and peaceful nature make them a great addition to specialized reef tanks.
Why Choose a Twinspot Goby?
✔ One of the most unique gobies, featuring eye-like dorsal fins for predator confusion.
✔ Beneficial sand sifter, keeping the substrate clean and oxygenated.
✔ Pairs well with other peaceful tank mates, making them great for community tanks.
✔ Hardy and adaptable, once properly acclimated and provided with a suitable diet.
✔ Can live long lives, up to 5 years in captivity with proper care.
⚠ Important Considerations Before Buying a Twinspot Goby:
🚫 Needs a mature sand bed with abundant microfauna – Not ideal for new tanks.
🚫 Can be challenging to feed – May require live foods initially.
🚫 Burrowing behavior may shift aquascape – Secure corals and rockwork properly.
🚫 Best kept in pairs – But must be bonded to avoid aggression.
Would you like another goby species covered? Let me know which one!