Yellow watchman goby

Geographic Origin and Biotope: Western Indo-Pacific Ocean. Inhabits shallow lagoons, sandy bottoms near coral reefs and sheltered bays where it digs deep burrows in the sand.

Taxonomy and Morphology: Yellow Watchman Goby (Cryptocentrus cinctus). Marine fish of the Gobiidae family (gobies). Elongated cylindrical body, large eyes placed high up for a 360-degree view and a large mouth.

Social Behavior: Famous for its mutualistic symbiosis with pistol shrimp (e.g. Alpheus bellulus). The nearly blind shrimp digs and maintains the burrow, while the goby acts as a "watchman" warning its roommate of dangers.

Coloration and Sexual Dimorphism: Often bright yellow with small blue spots on the head and fins. However, there is a gray/light brown ecotype, which fish can sometimes assume spontaneously. No obvious sexual dimorphism.

Aquarium Setup: Marine reef or fish-only aquarium (minimum 100 liters / 25 gallons). Mandatory a deep layer (at least 5-7 cm / 2-3 inches) of fine or mixed coral sand and stable live rocks at the base to allow digging the burrow without collapses.

Diet and Feeding: Carnivore. In nature it catches invertebrates and zooplankton. In the aquarium it should be fed with brine shrimp, mysis, chopped krill and fish eggs. Accepts sinking granular feeds specific for carnivorous marines.

Water Quality: Very robust marine species, excellent for beginners. Standard reef parameters: specific gravity 1.023-1.025, excellent skimming. Fears only the stagnation of pollutants on the bottom.

Compatibility and Tankmates: Peaceful with free-swimming fish (e.g. clownfish, damselfish). Very territorial towards other benthic gobies. Absolutely harmless to corals (Reef Safe) and ornamental invertebrates.

Aquarium Reproduction: Difficult, but possible. They lay adhesive egg masses in the ceiling of the underground burrow, constantly guarded by the male until hatching. Raising the pelagic larvae requires rotifers.

Risks and Diseases: Tendency to jump at lightning speed if frightened (lid or net mandatory). Risk of fatal crushing if the rocks do not rest on the bottom glass but on the sand.