Fish of the week #3-Synchiropus splendidus-Green mandarin


Sir Brian The Lenient
Staff member
RC Mod
Synchiropus spendidus Green mandarinfish

Mistakenly called gobies by some aquarists, the s. splendidus is a very popular addition to aquariums, as it is a beautiful fish and readily available. Unfortunately, the new keeper of the mandarin most often is forced to watch the fish slowly starve and die.

These fish are slow, methodical eaters and dine almost exclusively on live prey in the sand bed and on live rock. They will sometimes take prepared foods and live brine, but still require an abundance of copepods and microcrustacea in the sandbed/liverock as they will feed 24/7 in the tank. They should only be introduced in tanks that can meet these criteria. Newly set-up tanks or barren tanks will usually mean death for the fish.

The mandarin is completely reef safe and does not pay attention to other species. However, any fish with similar feeding habits (some wrasses esp.) should not be placed in the same tank unless there is ample food available for both.

Two males cannot normally be placed in the same tank, as they will fight to the death. The males are differentiated from females from a longer first dorsal fin. A male/female will sometimes pair up and have been known to spawn in captivity.

[This message has been edited by BrianD (edited 08-14-2000).]
Personal experience

One month ago, I had 3 male mandarins in my 180. I had one for over 16 months, one for about a year, and the third for about 4 months. Three males is a no-no, but I inherited the last two fish from tanks that they were doing poorly in. They would have died without intervention, so I thought they couldn't do any worse in my 180. For whatever reason, they coexisted fine for all this time until I rearranged and moved some rockwork. When I did that, they all started fighting. I thought they would kill each other, but I was lucky that two days in a row one ended up in the overlflow. I moved these two to my 125, which turned out to be a mistake because one of them ended up being sucked into an overflow and dying :(. I was depressed because he was just a skeleton when I got him and he recovered to look great.

Anyway, I have a very deep sand bed and a quite a bit of rockwork in both my tanks (especially in the 180). I have added detritivore kits and live sand activator kits to both tanks. I also set up a 30 gallon tank as a "seed tank" to allow copepods to multiply without predation, and then transferred them to my main tanks. My rockwork and sandbed is crawling with pods.

My two remaining mandarins are fat and beautiful, and they are my pride and joy. It is rewarding to keep them healthy. To me, in the proper setting, they are very easy to keep because you don't have to worry about feeding them. An active, live tank will provide all the food they need.

I have had a Mandarin Dragonette in my 120 reef since October, 99. He is so far in perfect health. The tank has over 200# of LR, and 1-2" of livesand, with a det kit. Tons of little creatures for him to graze on...

He was doing so well, that after 6 months I added another variety (spotted)and although coexisting, they never got along well. I noticed the pod population declining and the newer one was getting pretty thin, so I traded to another reefer. The pods have come back, and all is well.

I read a post on another board which said that they will slowly die over a year or two, even with live food. Dunno 'bout that.

<A HREF="" TARGET=_blank>
Thanks for the input, Playfair.

I'm curious. What was the sex of each of the species for mandarin?

Also, if they are only supposed to live a year, I have two that are on borrowed time :)

Russell, that is a very debatable issue. The size of the tank isn't as important as the life it contains. Scott Michael lists a 20 gallon tank as the minimum size. Most reefers would shudder at this suggestion. A 20 gallon tank full of live rock, a deep sand bed, and a refugium may handle a mandarin. It depends completely on how "alive" the tank is, and whether the pods and microcrustecea can maintain their population levels.

A 300 gallon tank with minimal liverock and no sand bed is an inferior home (for a mandarin) than the above mentioned 20 gallon tank. Again, the environment, not tank size, is the much more important criteria. Obviously, the larger the tank the easier it is to maintain levels without special additions such as a refugium.

Also curious, my 110 has tons of pods (i.e. I can see them clearly on the glass, on the plants, in the sand, they're everywhere). Did you notice a decrease in the amount of pods you saw? In effect do these guys eat a lot, would they be very detrimental to your DSB population or just "skim off the top"?
Yeah My 30 gallon is the same...I see tons of pods all over the glass and little critters swimming around the tank would I know if I can keep a mandarin?
My Experience

The first mandarin was in my very first salt tank, a 75 FO that I still have. I put him in before the tank was even done cycling. :( Also, he survived a copper treatment for ich on other fish. (This was when I was even more stupid and ignorant than I am now) I had no live rock in the tank for the first 3 or 4 months, then added about 30 pounds. He lived for about 6 months, then started to be harassed by a coral beauty to the point that he would no longer come out to graze. He just disappeared, I'm sure he starved to death.
Lesson one: Don't put them in with agressive fish.

I was without a mandarin for about a year and a half. In that time I set up a 40 gallon tank with the sole purpose of keeping a mandarin, and goniopora. It had about 75 pounds of live rock, and a macro-algae refugium, no other fish or shrimp. After it was crawling with pods I put in the mandarin. I had quite a bit of water movement in the tank, and one day I could not find the mandarin. I searched high and low, even the sump and plumbing. No mandarin. After about three weeks (and several more searches) he turned up in my sump, colorless and thin. I put him back in the main tank, covered the overflows, and cut down on the water circulation a bit. He fattened up again and thrived for another year. This mandarin would also eat some prepared foods, especially bloodworms soaked in Selcon.
Lesson two: Either keep the water movement fairly calm, or make sure the overflows are well covered. They are not strong swimmers unless alarmed, and are very susceptible to making unplanned trips to the sump.
Lesson three: These are tough fish if you get a healthy one to begin with. They do have a very limited diet, though, so if you can get one that is eating prepared foods, your chances of keeping them alive are much better.

Then I set up the infamous 125 gallon reef, and thought I would do Mandy a favor--I moved him to the new, bigger tank with loads of live rock and another refugium. Three days later the tank's front pane of glass broke. Mandy was one of the casualties.
Lesson four: If it ain't broke, don't fix it.

I just recently got my 135 up and running, there will be a mandarin in there after it develops a sufficient mandarin-food population.

I have never seen a mandarin eat an adult copepod, or pod of any sort, for that matter. I have sat for hours and watched them pick microscopic critters off of the rocks, sand, and glass, though. Some people (I belive Ron is one of them) believe they are eating juvenile copepods, etc.)

From all reports, most of them do not eat prepared foods.

Macro-algae refugiums, IMO, help a lot in keeping these fish. Not only do the 'pods grow like crazy in these places, but I believe it does something "magical" to the water. :) In other words, I think water quality is improved.

Anyway, that's been my experience with them. Probably the coolest marine fish, IMO.

Larry M

"My Dad could build--or fix--anything. Just give him a hammer, a saw, a piece of wire, and a stick. Then get the hell out of the way."
In response to the question, "Where did you learn how to do that?"

See my tanks at Northern Reef

[This message has been edited by Larry M (edited 08-14-2000).]
Larry thanks for the informative long does it usually take for a good amount of pods to be avaliable for these amazing fish. I have only had my tank running for 2 and a half months but there are tons of pods all over the glass and critters swimming around all over the mature should the tank be to keep these guys.

Russell--Like anything else, "mature" means different things to different people. It sounds like you have a good population of critters, but the question is: Will they be able to sustain a suitable population with the mandarin feeding on them? Also, do you have other fish in the tank? Any shrimp or other animals that may compete with the mandarin for food? Do you have a macroalgae refugium, or the ability to add one to your tank?

A 30 gallon tank is pretty small, and if I told you it was fine I'd probably get a bunch of nasty emails. :) But I think under the right conditions, with the right person watching the tank, and (more importantly) if you manage to get a healthy mandarin to put in there, then IMO it might be possible.

Larry M

"My Dad could build--or fix--anything. Just give him a hammer, a saw, a piece of wire, and a stick. Then get the hell out of the way."
In response to the question, "Where did you learn how to do that?"

See my tanks at Northern Reef
Great input, Larry. Thanks.

Gammarus shrimp are listed as a normal food source for mandarins, so I think they probably do supplement their diet on food sources other than copepods. One of my mandarins will normally eat thawed brine when it drifts by him, so a grammarus would be a nice snack.

Two thoughts on keeping a sizeable population (in addition to the refugium, as Larry discusses):

One If you have access to it, get some caluerpa in your tank and allow it to grow. Pods will multiply unchecked in the algae, and the mandarin will pick through it. I have a very stringy caluerpa in my 125, and it is crawling with life. Hair algae is also great for this (if you keep it under control :) ) You can also keep it in your sump and develop a population there.

Two Place some small pieces of quarter-inch PVC in your tank behind the rockwork. This is a perfect breeding ground for mysid and gamarrus shrimp. Bury it about halfway in the sand bed, and it will work great.

For a link to some great detritivore/sand bed flora/fauna kits, try

Larry, I can really relate to your if it ain't broke..... I thought I was doing everyone a favor by rearranging the rockwork and improving water flow, but all I did was disrupt some well-established territories.

Well, I have 2 coral banded shrimp that I am getting ready to remove. I also have a cleaner shrimp that will stay, but I have no fish yet. I have some corals and a cleanup crew also, so it seems as though it would be ok for him but if i ever do it i will probably wait for a while. I definately don't want the little guy to starve. Thanks.
I think it is worth emphasizing the prepared food bit again, too. IMO it is worth checking around, calling MO companies that you trust, etc, to see if they have a mandarin that will eat any kind of prepared food. I let mine eat what was in the tank whenever possible because I felt it was a more natural food source, but it was nice when necessary (like after the sump trip) to be able to fatten him up on Selcon-soaked foods. Brine shrimp, blood/blackworms, whatever.....they can all be boosted with vitamins and the such.

Larry M

"My Dad could build--or fix--anything. Just give him a hammer, a saw, a piece of wire, and a stick. Then get the hell out of the way."
In response to the question, "Where did you learn how to do that?"

See my tanks at Northern Reef
Sorry, Greenbud, forgot about your question.

If you do see any decline in population, you probably don't have sufficient capacity in your tank. The mandarin will feed off the live rock and the top of the sand bed. They don't "dig" into the sand bed for food. They hover over the sand bed for any movement of prey, and then they strike.

I rarely see my mandarin feeding off the sand bed. 99% of the time it is hovering around the live rock.

Brian, I'm not sure what sex they are... The one in my tank had a really long dorsal fin spike, but it had been "trimmed" by some other creature prior to this pic. The other one always had a short fin spike.


Gb, I don't notice any drop now, but having two definitely had an impact.

Russel, to answer your question, I think it took about 6 months. What you think are a lot now will die down as the population stabilizes.

[This message has been edited by Playfair (edited 08-15-2000).]
Nice pics, Playfair. I would call that mandarin on the left a male, due to the spike on the dorsal fin. The one on the right, of course, is a different mandarinfish, picturatus.

Larry M

"My Dad could build--or fix--anything. Just give him a hammer, a saw, a piece of wire, and a stick. Then get the hell out of the way."
In response to the question, "Where did you learn how to do that?"

See my tanks at Northern Reef
Great pics, Playfair.

I think the MO and LFS will see a spike in mandarin sales after people see those pics. Let's just hope they paid attention to the rest of the thread :D


Good job with these posts. I am sure you are only using this phrase to mean "much of the time," but in case you aren't, mandarins do not feed off the rocks 24/7. When the lights go out, so do the mandarins. Mandarins are kind of funny looking when they sleep because they turn very pale.