Green Mandarinfish: Gorgeous, Good-Natured, and a Very Finicky Feeder

Green mandarinfish (Synchiropus splendidus)

Green mandarinfish (Synchiropus splendidus)

Many coral reef fishes are renowned for their spectacular coloration and patterning, but there’s one particular species, commonly available in the marine aquarium hobby, that arguably surpasses them all in this regard. I’m talking about the green mandarinfish (Synchiropus splendidus).

Also known as the mandarin goby (though it’s a dragonet from the family Callionymidae, not a true gobiid), blue mandarinfish, splendid mandarinfish, or simply the mandarinfish, S. splendidus is really indescribable, exhibiting psychedelic swirls, lines, and spots of green, orange, blue, red, and yellow. But, frankly, I can’t do justice to this species’ otherworldly beauty with mere words. To really appreciate it, you just have to look at the accompanying photo or a living specimen.

In addition to its stunning coloration, the green mandarinfish possesses comically bulging eyes and a tiny mouth (which hints at its dietary requirements—more on this ahead). Also, this species is sexually dimorphic, with males generally being larger than females and sporting a greatly extended first dorsal spine. The common maximum length for the green mandarin is about 2½ inches.

Another splendid Synchiropus species

I should point out that S. splendidus has an equally psychedelic, similarly sized congener that you might come across at your local fish store—Synchiropus picturatus, commonly known as the spotted mandarinfish, the psychedelic mandarinfish, or, confusingly, the green mandarinfish. The care requirements for both species are pretty much identical, so the following information on S. splendidus applies just as well to S. picturatus as far as aquarium keeping is concerned.

Aquatic hummingbird

Perhaps the term most frequently used by hobbyists to describe S. splendidus is “hummingbird-like.” And that’s probably as accurate an analogy as one can provide. This fish typically hovers and flits from rock to rock, rapidly fluttering its pectoral fins, in search of the tiny crustaceans and worms that comprise its natural diet—looking very much like a hummingbird or bee flying from flower to flower in search of nectar.

Good news, bad news

S. splendidus is what I would describe as a “good-news-bad-news” species from the standpoint of aquarium keeping. The good news is, it’s a peaceful, well-behaved fish (with the exception of multiple males kept together) that generally ignores its tankmates. Also, owing to this species’ heavy body-slime production, it tends to be resistant—though, contrary to popular misconception, not immune—to certain ectoparasites, such as Cryptocaryon irritans (“marine ich”).

S. splendidus hovers much like a hummingbird while hunting for their next meal

S. splendidus hovers much like a hummingbird while hunting for their next meal

Now for the bad news: S. splendidus has one particular “Achilles heel” that cannot be overlooked or downplayed—it is notorious for starving to death in captivity. You see, wild-caught specimens very seldom learn to accept any food other than live, tiny invertebrates, such as amphipods and copepods (“pods” in hobby parlance). Some do take to non-living foods, such as frozen mysis shrimp, but you can’t depend on it. Even when live pods are available in abundance in an aquarium system, mandarins have the tendency to eradicate them over time, which leaves them vulnerable to starvation.

Does this feeding limitation mean S. splendidus can’t be kept successfully in aquariums? Well, not necessarily. There definitely are hobbyists who succeed in keeping the green mandarin. However, they don’t owe their success to luck or happenstance. They succeed because they make every effort to provide a suitable system and to sustain an ongoing supply of pods.

Providing enough pods

Quality live rock is typically crawling with pods, so any aquarium housing a mandarinfish must contain an ample quantity of it. In fact, the more live rock, the merrier. For reference, I once kept a green mandarin in a 75-gallon tank with 90 pounds of live rock, and it still managed to pick it clean of pods over time.

What that should tell you is, if you plan to keep a mandarin, it will likely be necessary to replenish the pod population in its tank on a regular basis—even if that tank is fairly large and fairly stuffed with live rock. To achieve this, you can/should:

  • Rotate in new pieces of live rock from time to time.
  • Actually introduce live amphipods and copepods, which are available from a number of retailers (LFS and online vendors).
  • Add a productive refugium to your system. This is essentially a separate tank or sump that’s connected to your display tank and shares the same system water. Its purpose (in this case) is to provide a safe, fish-free haven for pods to proliferate. As water is pumped or flows into the display tank from the refugium, pods will occasionally be swept into the display tank, thus bolstering the population there.
  • Avoid adding other fish species that will compete with the mandarin for the same microfauna food source.

Whatever methods you use to sustain the pod population, it’s still important to keep a close eye on your mandarin to ensure it’s getting enough to eat. You don’t want to see your specimen behaving lethargically or developing a pinched-in belly (check for this symptom at the time of purchase, as well). These are clear evidence of advanced starvation.

Captive-bred mandarins

A very exciting development in our hobby in recent years was the successful captive breeding of mandarins. Captive-bred specimens may be more costly than their wild-caught counterparts, but they have the significant advantage of being raised on commercially available, non-living foods. Thus, they should be considerably easier for hobbyists to feed. That’s not to say they’re “bulletproof,” but I would give captive-bred mandarins much better odds of long-term survival in an aquarium environment.

What’s your mandarin experience?
If you’ve ever kept a mandarinfish, whether wild-caught or captive-bred, please share your experiences—good, bad, or indifferent—with your fellow salties in the comments section below.


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About Jeff Kurtz

Jeff Kurtz is the Co-founder/Editor of Saltwater Smarts, former Senior Consulting Editor for Tropical Fish Hobbyist Magazine, and the aquarist formerly known as “The Salt Creep.” He has been an aquarium hobbyist for over 30 years and is an avid scuba diver.


  1. I lost my first Mandarin to starvation years ago but have a lovely one now for five years that eats frozen mysis, blood worm and pellets of various types. She’s doing great.

    • Jeff Kurtz says

      That’s great to hear, Ron! Was your new specimen wild-collected or captive-bred? Also, is there any difference in your husbandry approach this time around? We’d love to hear any advice you might have that could help others succeed with this finicky feeder!

  2. Lisa Foster says

    My mandarin, Spike, is doing very well. I’ve had him for at least four months now and he’s filled-out and active. He gets a fresh bottle of live copepods added to his tank every month, and he appears to be startingto understand frozens. I’m going to buy him nutramar ova next moth and see how he takes to it; hopefully it will speed the process of frozens conversion, because this guy is costing me $30 a month to feed and he’s not even half his adult size yet!!

    I would not get rid of my little buddy. I love him. However, I will absolutely never buy another unless I observe it eating frozens and/or pellets before purchase.

    • Jeff Kurtz says

      $30 per month is definitely a tough pill to swallow, but I completely understand your devotion to your mandarin. They’re really such beauties. Best of luck on the conversion to non-living foods, and keep us posted on Spike’s progress.

      • I just now found your reply (oops!!) Unfortunately, my dear Spike passed away in a terrible tank crash a couple of years ago. When he passed, however, he was in great health and had taken to, of all things, pellets! New Life Spectrum Small Fish was accepted within two or three months, and he was eating it regularly by about the fourth month – good news for my wallet! I stopped adding pods once he was well-adapted, and usually I would consider that a bad idea, but as long as he lived he stayed active, well-colored, and a healthy weight. I miss him so bad….he got a kiss before I flushed him that terrible morning of finding every fish dead. For reference to anyone else trying, he shared a 20g with two very young CB ocellaris clowns.

        • Jeff Kurtz says

          No worries, Lisa! So sorry to hear about your mandarin. Maybe you’ll luck out again with a specimen that takes to pellets.

          • Thought you might like to know that it just so happens I HAVE found another who is taking to the pellets (NLS Small Fish, again.) Must be something about those particular ones that they like…

            Both were purchased from Deep Sea Creations in Temecula, CA. My favorite ever LFS <3

          • That’s great, Lisa! I’m definitely a big fan of NLS products!

  3. Elias Ortiz says

    This is one of my favorite fish.i have yet to have one, im only running a ten gallon, but if i upgrade ill definitely be considering one!
    Good read guys!

    • Chris Aldrich says

      Hi Elias! Glad you enjoyed this post.

      They’re certainly beautiful fish! If (when) you upgrade in the future, keep an eye out for a captive-bred specimen. Their dietary demands are typically more conducive to long-term survival compared to their wild-caught kin.

  4. I have two of these, in my tank and are doing great , they’ve learns to eat frozen food , with patients it can be done

    • Jeff Kurtz says

      Ah, that’s an encouraging step in the right direction, Adrian! Keep experimenting with different foods to ensure your mandarin is getting adequate nutrition.

  5. Ive kept a spotted mandarin for a year now, i was a baby when i putchased it and was looking for food aggresivly in the shop. All it really eats now is frozen brine shrimp and frozen mysis, i add lobster eggs and cyclops now and again and sometimes live brine shrimp which it doesnt eat and put afew bags of copepods in now and again , some i worry if its getting enough to eat but it look that fat its like pat butcher worried if it gets any bigger for its size it might explode

  6. FlameAngelfish says

    You will NOT believe this… but my pair of mandarinfish REFUSE LIVE FOOD! :O
    Ravenous predators of pellets, frozen food, pellets, freeze-dried food, and pellets. They’re wild-caught too… I never knew my training techniques were so effective! I put gut-loaded copepods in the specimen box and dunk in the mandarinfish. It gulps the ‘pods down but spits them out, looking at me like “Hey! These are moving! “What in the world are these things!” Glad that I won’t have to train them onto live food! 🙂

  7. The mandarin fish is hands down my favorite fish. I’ve had my male mandarin, Bruce, for over two years now, and he’s now eating pellets. I recently bought a female and I’m in the process of getting her to eat foods other than live. Once she is eating pellets, I’ll introduce them and with a little luck try my hand at breeding them. We’ll see 🙂

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