Pholidichthys leucotaenia (Engineer Goby / Convict Blenny)
• Small fish safe: ✅ Yes
• Small invert safe: ✅ Yes
• Coral safe: ✅ Yes
• Minimum tank size: 150L+ (preferably 200L+ for groups)
• Adult size: ~34 cm (13 inches)
• Diet: Carnivorous (marine pellets, frozen mysis/brine shrimp, finely chopped seafood)
• Be aware of: Not a true goby or blenny—belongs to the family Pholidichthyidae. Rearranges substrate by digging extensive burrows, potentially disrupting corals or structures in the tank. Juveniles resemble schooling catfish but change appearance as they mature.
Engineer Goby (Pholidichthys leucotaenia) – A Fascinating and Active Burrower
The Engineer Goby, also known as the Convict Blenny, is a unique and visually deceptive species that undergoes a remarkable transformation as it matures. Despite its common name, it is not a true goby or blenny but rather a member of the Pholidichthyidae family. Engineer Gobies are highly active burrowers, constantly shifting sand and small rocks, which can help aerate the substrate but may also disrupt corals or tank decorations.
Appearance and Coloration
One of the most striking features of the Engineer Goby is its dramatic color and shape change as it grows:
• Juveniles (up to ~4 inches):
• Resemble schooling catfish, with horizontal black and white stripes running along their bodies.
• Often swim together in tight formations, mimicking a catfish school to deter predators.
• Adults (4 inches and larger):
• Develop vertical black and white bands, giving them a completely different look.
• Become more secretive and burrow-dependent, spending much of their time digging tunnels.
• Can grow up to 13 inches (34 cm) in captivity, making them one of the largest “goby-like” species kept in aquariums.
Natural Habitat and Behaviour
Native to the Indo-Pacific region, Engineer Gobies inhabit sandy lagoon reefs and rubble zones, where they:
• Dig extensive burrow networks beneath rocks, sand, and coral rubble.
• Live in large social groups as juveniles, mimicking schooling catfish for protection.
• Become more solitary or pair-bonded as adults, relying on their burrow for safety.
• Constantly shift substrate, moving sand and small rocks to expand their tunnels.
In captivity, they retain their burrowing nature, making them excellent sand-bed aerators but also a potential challenge for aquascaping.
Tank Requirements and Water Parameters
Engineer Gobies are resilient and adaptable, but they require plenty of space and substrate depth for burrowing.
• Minimum tank size: 150L+ (200L+ recommended for groups)
• Temperature: 24–27°C (75–81°F)
• pH: 8.1–8.4
• Salinity: 1.020–1.025
• Water movement: Moderate to strong
• Filtration: High-quality filtration and regular water changes to maintain stable conditions.
A deep sand bed (2+ inches) with rock structures is ideal, allowing them to build and reinforce burrows without collapsing tunnels. Be sure to secure all rocks and corals, as their digging can destabilize unsteady structures.
Diet and Feeding
Engineer Gobies are carnivorous and thrive on a protein-rich diet.
Recommended foods include:
• Frozen mysis and brine shrimp – Their primary diet in captivity.
• High-quality marine pellets and flakes – Enriched formulas for optimal health.
• Finely chopped seafood (shrimp, squid, or fish) – Occasional treats.
• Live foods (copepods, amphipods, or blackworms) – Encourages natural foraging behavior.
Feed 1-2 times daily, ensuring food reaches their burrow, as they prefer to stay near their tunnels rather than chase food in open water.
Compatibility and Tank Mates
Engineer Gobies are peaceful and reef-safe, making them great for:
✔ Tangs, Angelfish, Wrasses, Basslets, Clownfish, and Blennies.
✔ Other Engineer Gobies, if introduced together—best kept in groups as juveniles or pairs as adults.
✔ Reef-safe invertebrates, including shrimp, snails, and crabs.
Avoid housing with:
❌ Large, aggressive fish (e.g., Triggerfish, aggressive Dottybacks, large Wrasses) that may harass them.
❌ Very small shrimp, as larger Engineer Gobies may occasionally eat them.
❌ Fish that depend on a stable rock structure, as burrowing may disrupt their habitat.
Burrowing and Tank Considerations
Engineer Gobies are expert diggers and will:
• Rearrange the substrate daily, potentially covering corals or destabilizing rocks.
• Build interconnected burrows, creating tunnels beneath the sand bed.
• Occasionally spit out sand into the water column, requiring good filtration.
To prevent tank damage from their burrowing:
✔ Secure all rocks and corals firmly to prevent collapse.
✔ Provide a deep sand bed (2+ inches) for stable burrow construction.
✔ Use a mix of fine sand and rubble, which helps support tunnels.
Health and Disease Considerations
Engineer Gobies are hardy, but they can be susceptible to:
• Marine Ich (Cryptocaryon irritans) – They are resilient but can carry parasites.
• Bacterial infections – Often caused by injuries from burrowing near sharp rocks.
• Malnutrition – Ensure they receive enough food, as they are not strong swimmers.
To keep them healthy:
✔ Provide a varied diet rich in protein.
✔ Ensure stable water parameters.
✔ Quarantine new fish before adding them to the main tank.
Lifespan and Long-Term Care
With proper care, Engineer Gobies can live up to 5-10 years in captivity. Their constant activity, burrowing behavior, and transformation from juvenile to adult make them a highly rewarding species to observe.
Why Choose an Engineer Goby?
✔ Unique transformation – Changes from a horizontally striped juvenile to a vertically banded adult.
✔ Great for sand bed aeration – Constantly digging and shifting substrate.
✔ Hardy and peaceful, making them ideal for reef tanks.
✔ Can live in groups, especially when young.
✔ Fascinating and active, always engaging with their environment.
⚠ Important Considerations Before Buying an Engineer Goby:
🚫 Burrows extensively – Can destabilize rock structures and cover corals with sand.
🚫 Needs a deep sand bed – A shallow substrate may not allow proper burrowing.
🚫 Best kept in groups as juveniles, but adults may become more solitary.