Mandarin Fish | Care And Feeding

Mandarin fish, namely the Spotted Psychedelic Mandarin (Synchiropus picturatus) and the Splendid Mandarinfish (Synchiropus splendidus), are some of the most beautiful and exotic fish available in the marine aquarium hobby.

But sadly, Mandarin fish, or Mandarin dragonets as they are otherwise known, are difficult fish to keep alive in captivity.

mandarin fish

Mandarins – secretive, but always amusing

In the wild, Mandarins are bottom-dwelling and feed exclusively on small live foods like copepods and small worms and crustaceans.  It is this specific diet of live foods that makes them so difficult to maintain in our aquariums.  Most die of malnutrition and starvation within 3 months, if not sooner.

If Mandarin fish are to be kept with any degree of success, they should be kept in mature, well-established reef aquariums with plenty of live rock and live sand on which they can forage for food.  Because of their food requirements, the minimum size aquarium for keeping a single Mandarin fish should be about 75 to 90 gallons and with a sump or refugium.  The aquarium should be mature and well-established with a healthy population of small worms and copepods.  Aquariums with plenty of live rock and that are at least 2 years old are preferred.  Mandarin fish can decimate the copepod population of a new, immature reef tank in a matter of days.

Training Mandarin Fish To Accept Frozen Foods

I have trained two Splendid Mandarin fish to accept frozen mysis shrimp.  A third Spotted Mandarin fish is a new addition as of this writing (March 2012), but it too is getting used to eating frozen mysis.  My first Mandarin has been with me for almost three years thus far.

So how did I train my Mandarin fish to eat frozen foods?

Upon returning from the LFS, I acclimated my first Mandarin fish for one hour before placing it into a 10 gallon quarantine tank.  The quarantine tank was filled with a very thin layer of live sand from my main tank, along with three small pieces of live rock, just to help the fish feel more comfortable.  After a couple of hours, I noticed that the Mandarin was already starting to pick at ‘pods on the live rock.

‘Gut-Loading’ Brine Shrimp

I was told by my LFS that they were going to have a batch of live brine shrimp the following day.  Returning home, I placed the brine shrimp in a plastic container along with the water they came in and fed them a whole cube of Hikari brand Rotifers.  Hikari Rotifers are frozen rotifers and they are the ideal size for brine shrimp to feed on.  The brine shrimp immediately began to swarm the still-frozen cube in a feeding frenzy!

Feeding brine shrimp with rotifers or even plankton makes them more nourishing — live brine shrimp by themselves are a poor diet for marine fish.   In fact, some experts liken the nutritional value of live brine shrimp to a person eating a candy bar in place of a balanced meal.  ‘Gut-loading’ brine shrimp with rotifers makes them much more nutritious.

mandarin fish

Splendid Mandarin Fish

After the brine shrimp had consumed all of the rotifers, I aerated the water they were in with an air pump and a wooden air stone.   Aerating keeps live brine shrimp alive much longer than if the water wasn’t aerated.  I’ve had batches stay alive in the same water they came in for up to 5 days when aerated.  Using a wooden airstone creates very fine bubbles and in a way, acts very much like a protein skimmer.  The fine bubbles causes the waste matter from the brine shrimp to form a rim of scum just above the water-line!  My guess is that the brine shrimp live longer if they are not swimming in several days worth of their own waste.

Using a fine mesh plastic sieve, I transferred some of the gut-loaded brine shrimp to the Mandarin’s quarantine tank.  Mandarin fish prey on live food in the wild, so seeing brine shrimp swimming about the tank immediately engages their attention.  And without exception, they will always pursue and eat live brine shrimp.

Enriched brine shrimp should be fed to Mandarins in quarantine a few times a day and we want to get them to eat as much as they can.  Most Mandarins are malnourished by the time they reach the tanks in the LFS.  Think of it as a reward for the fish for making it through alive, after being shipped a couple of thousand miles in a small plastic bag crammed into a styrofoam box.

mandarin fish

Spotted Psychedelic Mandarin

Benefits Of Quarantining A Mandarin Fish

Mandarins are very cautious eaters.  They will spend a few seconds staring at their food, deciding on if they are going to eat it.  Now, if the brine shrimp were placed in the main display tank with several fast swimming, hungry fish, the brine shrimp would all be eaten before the Mandarin fish even got a bite.

Many people make the mistake of putting newly aquired Mandarins into their main display tank straight away.  They are more concerned with the fish being able to feed on the naturally occurring copepods on the live rock.

Quarantining the Mandarin for a couple of weeks ensures that the fish recuperates from shipping and gets to bulk up on gut-loaded brine shrimp before being put into the main display.  And you are quarantining all new fish to prevent the possibility of bringing in diseases like ich into your healthy display tank, right?

Introducing Frozen Mysis Shrimp To Mandarin Fish

Here comes the part where we will try to get our Mandarin to eat frozen mysis.  Thawing the frozen mysis first, of course..

Thaw a cube of frozen mysis in a cup of aquarium water — this is an important step.  Thawing mysis in tapwater will make them smell like chlorine which will cause wild-caught Mandarins to avoid them.

Put a few pieces of thawed mysis shrimp along with live brine shrimp into the tank.  Do this for a few days and the Mandarin will inadvertently eat some mysis along with the brine shrimp.

Soon, the Mandarin will start to associate thawed mysis with live brine shrimp.  After about two weeks, you can reduce the amount of live food and feed mostly mysis.  Gradually, you can replace the live food entirely with thawed mysis.

Placing The Mandarin Fish Into The Main Display Tank

After 2 weeks, and if our Mandarin fish has not shown any signs of disease, we can place it into the main display tank.   Proper acclimatisation to the water in the main display tank is important.

Release the Mandarin into a corner of the aquarium, away from the territory of other fish.  Most Mandarins will begin to swim amongst the live rock of a tank almost immediately.  It is almost like they are confident that their bright coloration will serve as enough of a warning to other fish that they have a poisonous mucus on their skin.  Indeed, not many fish will harrass a Mandarin!

Feeding A Mandarin Fish In The Main Display Tank

When feeding the general fish population in the main display tank, deposit some mysis into a quiet corner of the tank.  Since most fish actively pursue food in the middle of the water column, depositing mysis into a corner will allow the Mandarin to find them and eat in peace.  After some time, it will start to explore that particular corner of the tank every time it smells food, which is good as it will not have to compete for food with other fish.

My first Mandarin fish has even taken to eating pellets which I pre-soak in aquarium water.  I always make sure to put some pellets in his quiet corner of the tank whenever I feed the other fish.

But it should be noted that only a few Mandarin fish in captivity will take to eating pellets.

Increasing The Copepod Population In Your Tank

Mandarin fish keepers are often concerned about increasing the copepod population of the tank for the Mandarin to graze on.  Many purchase expensive bottles of live ‘pods from their LFS in the hope that they will multiply in the tank.  Most bottled live copepods sold commercially are of a species found in lower salinity water and will not survive for long, let alone reproduce, in the full salinity of a reef aquarium.

Your best bet to increasing the copepod population in your tank is to have several pieces of live rock in your sump or refugium along with some macroalgae like chaetomorpha.  You will usually find copepods intermingled in clumps of chaetomorpha algae.  Some copepods will eventually make it to the main display through the return pump.

I like to make sure that more ‘pods get into my main display by taking a handful of chaetomorpha (gloves on) from the refugium and swirling it around in the water of main display tank before putting it back in the sump.  I do this once or twice a week.  Don’t worry about the bits of sediment from the chaeto — they will settle after a few hours.

Mandarin Fish Compatibility

Mandarins are best kept with other docile fish, although they seem to do fine in FOWLR tanks with more aggressive species.  Just ensure that the Mandarin has a quiet corner in which to eat and lots of live rock for it to forage in.  Most other fish will usually leave Mandarins alone — in the wild, bright coloration is an indicator that the animal has some sort of toxin.  In the case of the Mandarin fish, it is a poisonous slime coating excreted from their scale-less skin.

Male Mandarins have a characteristic long spine on their dorsal fin.  Avoid putting two male Mandarins into the same aquarium as they will fight to the death — surprising behaviour from an otherwise extremely docile fish!

Female Mandarin fish lack the long spine and have a somewhat rounded dorsal fin.  From my experience, it is perfectly fine to introduce a female Mandarin into a male Mandarin’s tank, or vice versa.   Occasionally, you will find mated pairs of male and female Mandarins on sale but these are best left to expert aquarists with very large tanks of 200 gallons or more.

The docile nature of Mandarin fish also make them good tankmates for seahorses.

Captive-Bred Mandarin Fish

Mandarin fish have recently been successfully captive-bred and made available commercially.  Like captive-bred seahorses, captive-bred Mandarin fish have been raised on frozen mysis and are much easier for beginning or intermediate hobbyists to maintain unlike their wild-caught cousins.

Read more about:


How To Acclimate Fish

Quarantine Tank

Feeding Marine Fish


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