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Spotted Watchman Goby

Watchman gobies or Cryptocentrus cinctus belong to the family Gobiidae. This is a large family, comprised of over 2,000 species in 200 different genera. Members of this family are more commonly referred to as gobies. Gobies are one of the most popular fish among saltwater aquarium owners. Spotted watchmen are natives of the shallow watered regions of the Indo-Pacific. Significant populations can be found off the coasts of Australia.

Gobies are small, bottom dwelling fish. Even the largest members of the family Gobiidae only grows to about a foot in length. Watchmen are approximately half that size when fully grown. They have slender cylindrical shaped bodies with an almost worm-like appearance. The spotted watchman is most typically whitish to light gray in color with spots of varying size over their entire body. These spots may be pink, reddish or grey in color. The spots on their heads are frequently interspersed with smaller speckling.

Gobies are best known for their symbiotic relationships with small crustaceans, most especially pistol shrimp. They frequently cohabitate with these shrimp in sand burrows of the shrimp’s making. The watchman is no exception. They are given their names for the way in which they stand guard over their shared burrows while their roommates scurry about in the course of their daily activities. Although not nearly as adept at digging, gobies will borrow into the sand at night and to avoid predation in the absence of a companion shrimp. A sand substrate is a prerequisite for owning a goby. They will also require plenty of hiding place on the bottom of the aquarium to give them the confidence to stray away from their burrows in search of food.

Gobies in general make very interesting additions to any community tank or marine reef setup. It is simply fascinating to watch a fish and a crustacean merge in symbiotic harmony. These are benign species who take little interest in the affairs transpiring above them as long as their sand laden kingdom is not intruded upon. Gobies can be easily mixed with most crustaceans without any cause for concern. They do however exhibit territorial aggression toward other bottom dwelling fish. This species is among the most aggressive of its kind. They take their sentry duty very seriously. A mated pair works well together. Avoid having any other bottom dwelling fish in your aquarium unless it has a large bottom surface area.

Gobies have much better eyesight than their six legged counterparts. They will act as a seeing-eye-dog for their nearly blind companions. The sensory appendages on their heads (cirri) add a second level of security. They patiently stand guard while the shrimp busily excavates their burrows. When a predator draws near the watchman swishes it tail to alert the shrimp to imminent danger and they both quickly retreat into the sanctuary of their earthen abode.

A pistol shrimp may indeed dig several burrows around an aquarium until it creates the perfect one to call home. At the end of a hard days work a small rock or clump of sand will be pulled over the burrow opening to conceal its presence from nocturnal prowlers.

Both gobies and their life partners are carnivores. They can be fed mysis or vitamin enriched brine shrimp. They will also accept flake food, pellets and frozen preparations developed for marine carnivores.

A precautionary note in goby ownership: Although gobies are bottom dwellers by nature, they will on occasion indulge in brief interludes to the surface of an aquarium. They are accomplished jumpers. They must only be housed in a well lidded aquarium for their own protection.

Environmental Parameters


TemperaturepH LevelSpecific Gravity
72-78 °F8.1-8.41.020-1.025


This article was authored by S.J. Broy

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Document modified on Mon May 30 2:39:34 UTC 2011
Document created on Mon Jan 4 23:00:39 UTC 2010
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