Two spot gobies or Signigobius biocellatus are members of the family Gobiidae. This is a rather large family consisting of over 2,000 individual species in more than 200 genera. Two spots are indigenous to the Indo-Pacific. They range form the Philippines south to Australia.
This species has the elongated cylindrical body one would expect to find in a goby. One of the more interesting aspects of gobies is their wide variety of coloration and body patterning. Two spots are yet another example of these variations. Compared to the exotic coloration typical of many gobies, this species is rather bland in appearance. It has a light tan body splattered with brown and pale orange markings of various shapes and sizes. This coloration makes it blend in almost seamlessly against the backdrop of the ocean floor or while perched atop a rock formation. The most distinguishing characteristic of this species is its two dorsal fins. These fins stand erect on the fishes back. They are taller than the fish’s actual body. Each of theses fins has a large false eyespots meant to confuse predators. When this fish is viewed from the side, it looks very much as if you are staring into the face of a fish two to three times its size. It is these two eyespots (ocelli) for which the fish is named. These fish are also sold by the aquarium industry under the names; twinsspot goby, signal goby, and crabeye goby.
Two spots are bottom dwellers. As with many bottom dwellers, this is primarily a scavenger fish. These fish sift through sand in search of food. They are also burrowers. Two spots use their mouths to carry away sand and rubble in the construction of their burrows. An aquarium with an adequate supple of live rock and living sand as a substrate will emulate their natural habitat, provide them with a secondary food source, and prevent them from accidentally damaging themselves.
This is a small, exceptionally mild mannered fish. They only grow to an average length of 2.5 inches. They make wonderful additions to both multi-species and marine reef aquariums. These gobies should not be housed with larger or even moderately aggressive fish. Unlike most bottom dwellers, two spots are tolerant of other bottom dwelling fish. They may however exhibit territorial behavior toward conspecifics. A mated pair may be successfully housed together. Depending on the population of your aquarium, this species can be housed in as little as a 10 gallon tank. This is a short-lived species. Their average life span is only about two years. Two spots have a moderate care level. They can be raised by intermediate saltwater aquarists.
Two spots are carnivorous. They should take readily to flake food or pellets formulated for meat eaters. To keep them healthy and vigorous, their diets should be supplemented with mysid or brine shrimp or any other supplement commonly fed to marine carnivores. They should be fed 1-2 times daily.
Breeding Two Spot Gobies
In nature, this species is most commonly observed in pairs. They are monogamous by nature. Male-female couples cohabitate in the same burrow. A sexually mature fish will commonly starve itself to death if becomes separated from its life mate.
This species is known to spawn in captivity. Their mating habits are indeed quite unique. The female will first enter the burrow to deposit her eggs. She will then seal the male in the burrow for the eggs to be fertilized. The male will remain in the burrow for 2-3 days. During this time the female will periodically unseal the burrow and release the male. The male may eat or the couple may perform routine maintenance on the burrow. Once the objective has been achieved, the female will reseal the male in the burrow. Eventually the male will permanently exit the burrow. The couple will then construct another burrow or reopen a previously abandoned one. When the borrow that acted as a nursery is unsealed again, a single juvenile will emerge.