Dormitator maculatus (Fat Sleeper Goby)

Dormitator maculatus

Last updated on July 15th, 2022 at 03:13 am

You might not know it by name, but chances are you’ve probably seen the Fat Sleeper Goby (Dormitator maculatus). You just didn’t realize that you were looking at a fish! This furry-looking creature with large eyes and feathery fins has been spotted wandering around the Indo-Pacific waters of Thailand, Malaysia, Indonesia, Australia, and Papua New Guinea.

It’s not an uncommon sight in sandy environments with plenty of hiding places like mangroves and coral reefs. If you live in an area where this fish lives, chances are you’ve seen one before!

Impossible as it may seem, there’s actually a fish in the sea that becomes fatter and fatter with every meal it eats. The Fat Sleeper Goby – also known as Dormitator maculatus – uses its bulging belly to attract unsuspecting prey and then gives them no other option but to eat him whole.

Origin and descriptions

Dormitator maculatus

Dormitator maculatus are native to Southeast Asia and have since been introduced to California where they have become invasive. It is currently ranked as one of California’s top 100 most harmful invasive species. This fish can live in both saltwater and freshwater; it needs a lot of room to live and breed. The dormitor grows up to 2 inches long and can weigh up to 3 pounds.

They eat small invertebrates that live on rocks or plants near shorelines, but will also eat smaller fish if given the chance. The dormitor is usually not aggressive toward humans but you should be careful when handling them because their teeth are sharp enough to puncture skin easily.

If your dormitor does get out of its tank and into your house, it may hide behind furniture or under carpets for days before you even notice its presence. If you do find a fat sleeper in your home don’t try to pick it up with your bare hands! Instead, use tongs or grab something plastic like a margarine tub lid then scoop him into his tank. If he gets too big for his tank, he will start eating other fish so make sure his tank is big enough from day one!

Dalmatian Lyretail Molly (Poecilia latipinna)

Species profile

Dormitator maculatus belongs to the family of Eleotridae, or sleeper gobies. The name sleeper goby comes from their tendency to remain motionless for long periods of time, even when removed from the water. They can grow up to 2 inches in length and are found primarily in Australia and New Guinea. They live in streams, rivers, and ponds and eat algae, insects, fish eggs, worms, small crustaceans, plants, and detritus.

Dormitator maculatus is a species of goby that is native to marine, fresh, and brackish waters along Australia’s coastline. This fish gets its name from its sluggish behavior and tendency to sleep during low tide. It’s relatively small size and sleeps so much throughout its life cycle that it can easily double in size within a year.

Common names

Dormitator maculatus goes by many names, some of which are fat sleeper goby, jade goby, jade sleeper goby, striped sleeper goby, or just sleeper goby.


The Dormitator maculatus, also known as Fat Sleeper Goby, is a marine fish native to Indo-Pacific waters. This species prefers tropical marine conditions and occurs on reefs at depths between 8 and 20 meters. The name fat sleeper goby is due to its appearance. These tiny creatures are nocturnal scavengers and have eyes located on top of their heads, enabling them to see above water when other fish cannot.

Their bodies are covered in numerous bumps that help camouflage them from predators while they sleep during daytime hours. They can live up to five years if properly cared for in captivity but will only survive about two years in their natural habitat.

Fat sleeper goby size

Dormitator maculatus

Female jade sleeper goby can grow up to an average size of 1.8 inches (4.6 cm) in length, while male jade sleeper goby grows slightly larger than the females, reaching an average length of 2 inches (5.1 cm).

Bumblebee Goby Fish (Brachygobius doriae)

Tank size

The minimum recommended tank size for this type of fish is 10 gallons (38 gallons)

Tank requirements

The dormitor and pygmy sleeper gobies are very sensitive to water quality, so they must be kept in a low-stress environment. The tank should have plenty of rocks or other structures to use as hiding places. A tight-fitting lid is also necessary because they can jump out of an uncovered tank. Dormitators prefer acidic conditions with a pH between 6.5 and 7.0 but will tolerate more neutral conditions.

They need good filtration that provides both mechanical and biological filtration; keep these fish in tanks without live plants due to their herbivorous diet. Lighting isn’t critical for these fish, but it’s still recommended for optimal coloration. Avoid keeping them with large, aggressive fish such as angelfish. For maximum lifespan, feed them small amounts three times per day.

Feed brine shrimp nauplii along with dried seaweed and algae wafers several times per week.

The dormitor goby has a distinctive body shape compared to other gobies: its belly is noticeably plumper than its head and tail regions.

Tank mates

Dormitator Maculatus is a fish that should be kept with other peaceful tank mates. Some options include Snowflake Eel, Bristlenose Pleco, and Bala Sharks. Do not house Dormitator Maculatus with aggressive or fast-moving fish.


Dormitator maculatus

Dormitator maculatus is generally easy to breed. You can tell males from females by looking at their dorsal fins: Males have pointed dorsal fins while females have rounded ones.

This species reproduces through external fertilization; males build nests using small pebbles and guard them until eggs are laid on top of them. Eggs are deposited on rocks or plants and guarded by both parents.

Brood size can be as high as 200 fries, but 50–100 is more common. Fry will eat newly hatched brine shrimp and rotifers. The parents will eat any unhatched eggs. The male will not take care of his offspring, so it’s important to remove him once spawning is complete.

Dwarf Indian Mudskipper (Periophthalmus novemradiatus)

They grow quickly, reaching 2.5 cm (1 in) within 6 months of hatching. They are sexually mature at 8 months of age, when they reach 5 cm (2 in).

Dormitators grow to about 2 inches long and should be kept in groups of five or more because they are very social fish that live in large schools in nature.

Are they aggressive or peaceful?

Dormitator maculatus, also known as fat sleeper goby, is a peaceful and active fish that shouldn’t be kept with other aggressive fish. These are large benthic fish that require plenty of space to swim around in. They will not start fights with their tank mates unless they feel threatened.

Dormitator maculatus care

Dormitator maculatus

Dormitator maculatus are one of three fish species in their genus, and they are also known as Fat Sleeper Gobies.

Their family was named so due to their larger size, they have an increased capacity for fat storage. Because of their bodies’ ability to store more energy than other goby species, these fish can live longer without food than other gobies.

Despite being able to survive on less food, dormitators should be fed often; otherwise, they will starve themselves until death. However, if overfed or kept in too small of an environment, dormitators may become obese and die from complications related to obesity such as heart failure or liver disease.

What they eat

They are omnivores, feeding on algae and sponges in their reef habitats. However, when living in captivity, they readily accept flake foods and frozen fish. A fat sleeper goby will generally eat about once a day.

If you feed them too much at one time, they may not eat for several days because of a stomach ache. They should be fed small amounts of food every other day or so to prevent overeating and an upset stomach.


They can live for 10-15 years when proper care is given to them.

Datnioides microlepis (The Indo Datnoid)

Parasites and diseases

Dormitator maculatus is an herbivorous species that don’t usually suffer from parasites, but it’s been known to suffer from Cryptocaryon irritans and Lepeophtheirus larvae.

Treatment for Lepeophtheirus larvae is more difficult since these infections are typically fatal if not treated in time. If you suspect your Fat Sleeper has contracted Lepeophtheirus larvae, you should take it to a vet immediately—do not try to treat it yourself!


Dormitator is known for being a slow-moving fish, so it’s an easy target for predators in its environment. That makes the fish pretty skittish and somewhat hard to breed in captivity.

Some common predators are moray eels, triggerfish, and other large fish.

When threatened, Dormitator will bury itself in sand or gravel to hide from predators. It also hides by burying itself in its host anemone’s tentacles.

Do Dormitator maculatus make good pets?

If you want a fish that’s easy to take care of, dormitator maculatus could be an excellent choice. These guys don’t eat much and prefer loner habits when it comes to schooling, so they won’t be challenging to keep in your tank. When cared for properly, dormitators grow to roughly 2 inches and can live over 10 years!

Dormitator maculatus are sensitive fish and should be kept in a tank that has excellent water quality, as well as strong filtration.