Green Mandarinfish
Green Mandarinfish

Green Mandarinfish

Synchiropus spendidus

Green Mandarinfish

The Green Mandarinfish (Synchiropus splendidus), commonly referred to as Mandarinfish only, belongs to the Dragonet family Callionymidae. The Chinese perch, Siniperca chuatsi, is sometimes called Mandarinfish, but these two species belong to different families (Callionymidae and Percichthyidae respectively) and are only distantly related.

The vibrant colours and intricate patterns displayed by the “psychedelic” Green Mandarinfish has made it a popular aquarium fish among marine aquarists and it is an important source of income for many local economies in South East Asia, especially in the Philippines. The fish is also utilized as food in Asia.

The Green Mandarinfish has not been evaluated for the IUCN Red List of Threatened Species.

Geographical distribution, habitat and habits

The Green Mandarinfish lives in the western Pacific Ocean and has been found in the waters of Australia, China (Taiwan), Indonesia, Japan, Malaysia, Micronesia, New Caledonia, Palau, Papua New Guinea, and the Philippines. The geographical range stretches from the Ryukyu Islands of Japan to Australia. This species is only found in tropical waters.   

The Green Mandarinfish inhabits inshore reefs and shallow protected lagoons, including silty bottoms with coral and rubble. The depth range for this species is 1-18 meters / 3.3-59 feet. The fish is primarily bottom dwelling, likes to stay in small groups or pairs and can hide under foliose (leaf-like) and dead coral.

Size and appearance

The largest scientifically measured Green Mandarinfish was 6 cm / 2.4 inches. The head of the Green Mandarinfish is broad and depressed. The fish is equipped with large pelvic fins that look like fans and these fins are used to walk over the bottom.

The Green Mandarinfish is a truly flamboyant fish and is sometimes referred to as “the psychedelic fish” due to its ostentatious colours and patterns. The body is decorated with intricate mosaic patterns in a wide range of contrasting colours, typically green, blue, yellow and orange red. In some specimens the ground colour is bright red, but this is very rare.

These fishes have no scales and their bodies are instead protected by a thick mucus coating. The coating exudes a repugnant smell and has a bitter taste. There is also a layer of sacciform cells on the skin which produce and release substances with some toxins. The toxins might be a way of repelling predators and competitors in the ocean, and the flamboyant colours of the Mandarinfish might be used to tell other animals about these toxins, a so called warning coloration.  

Green Mandarinfish care

The Green Mandarinfish is an extremely docile and friendly species and it should not be combined with aggressive species in the aquarium. Even species that leave the Green Mandarinfish alone can cause problems by gulping down all the food before the dawdling Mandarinfish gets a chance to catch any. Even though mandarins typically live in groups or pairs in the wild, they are known to be quite intolerant of their own species when kept in small aquariums. It is never a good idea to combine two males unless your aquarium is very big and cleverly decorated, because the fighting can result in severe injuries or even death.  

The Green Mandarinfish is considered reef safe, but it may nibble at small coral polyps. 
The recommended water temperature is 24-26° C / 75-79° F, the salinity should be around 1.025 and the pH-value as close to 8.3 as possible.

The aquarium where you keep your Green Mandarin should contain plenty of suitable hiding spots, such as caves and crevices. A Green Mandarinfish that is kept in a barren aquarium can become very stressed and shy. If you have a Mandarinfish that stays hidden all the time, try including even more hiding spots in the set up.

In the wild, the Green Mandarinfish is commonly found in areas subjected to powerful waves and streams and it is therefore reasonable to assume that they will appreciate similar, well aerated, conditions in the aquarium. It is however a good idea to turn off powerful pumps during the feeding time to make it easier for the sluggish Mandarinfish to catch any food.

Feeding Green Mandarinfish

The Green Mandarinfish searches for food on the bottom and will chiefly feed on small crustaceans, e.g. amphipods and isopods. They are also fond of protozoa and tiny aquatic worms.

Getting the Green Mandarinfish to eat in the aquarium can be tricky. Wild mandarins have an estimated life span of 10-15 years, but aquarium kept specimens will often die within 2-4 years since their keeper fails to get them to eat enough. It is also common among aquarists to keep their mandarins on a diet that isn’t very suitable for them.

If you want to keep Green Mandarinfish, you should ideally wait until you have a well established aquarium with plenty of live rock – at least 30 kg / 66 pounds per mandarin – because this will make it possible for the Green Mandarinfish to eat naturally occurring tiny animals and polyps just like it would do in the wild. Generally speaking, the aquarium should have been active for at least six months before you introduce any mandarins.

Ideally avoid using ozone- and ultraviolet filters in the aquarium when keeping Mandarinfish, because such filters can kill organisms necessary for a well functioning ecosystem that provides the mandarin fish suitable food. The tiny organisms killed by ozone- and ultraviolet filters are necessary as food for somewhat larger organisms, and the chain continues all the way up to copepods and other organisms on which the mandarins feed. It is also important to keep in mind that copepods go through a free-swimming stage during their lifecycle and during this stage they will be vulnerable to ozone and ultraviolet filters.

The naturally occurring fauna in the aquarium can be supplemented with meaty foods such as fish eggs, mosquito larvae and small shrimps. Only feed small foods, because the Green Mandarinfish has a rather small mouth. Some aquarists have trained their mandarins to accept frozen foods, but this is tricky.

As mentioned above, the Green Mandarinfish may nibble at small coral polyps.   

Breeding Green Mandarinfish

The Green Mandarinfish can be sexed based on size, because the males grow larger than the females. The male fish will also develop comparatively larger fins and his dorsal fin can be twice as big as her dorsal fin. The first dorsal spine is greatly elongated in males and will sometimes reach his caudal peduncle.

Spawning can occur weekly for several months and this species is capable of spawning year round. The Green Mandarinfish is a pelagic spawner that carries out external fertilization. When it is time to spawn, small groups and males and females will assemble during the night and spawning will typically take place about one meter (3 feet) above the reef. The male and female fish will swim upwards in the water, close to each other, when the eggs are released and fertilized.  

Each female can only spawn once per night and the males will compete with each other over available females. The female fish can produce from a dozen up to over 200 eggs per clutch and the eggs will be around 0.7-0.8 mm in diameter. The eggs are spherical and colourless and will drift around in the ocean until they hatch. In the beginning the eggs will be clumped together, but after a while they will start to slowly break up into smaller groups. The Green Mandarinfish does not care for or guard its offspring in any way.  

The incubation time is very short and the eggs will typically hatch after 12 hours. After no more than 36 hours after fertilization the eyes will have become pigmented and the mouth well developed. After about 2 weeks, the juveniles will be shaped like miniature copies of the adult fish with a large head and a triangular body. The orange brown colour and the green bands will appear when the fish is 18-21 days of age. The adult colouration develops during the second month when the fish is about 1-1.5 cm / 0.4-06 in long.    

The Green Mandarinfish has been successfully bred in captivity.

Dargonet articles

Spotted Mandarinfish – Guide to keeping Synchiropus picturatus
Starry Dragonet – Guide to keeping Synchiropus stellatus


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