Mandarin Goby:

Caring for a Mandarin Goby
(in a Nano Tank)

By Josh Day

Let's not beat around the bush. The purpose of this article is to discuss housing a mandarin goby in a nano reef tank, i.e. a 5-20 gallon saltwater aquarium. And you probably thought I couldn't get any more controversial...

Due to the heat on this topic, please forgive the following disclaimer. However, if you've ever had a passing interest in mandarins and possibly keeping one in a nano tank, you've no doubt seen the blatant hostility from all the nay-sayers out there. I've done a lot of reading about mandarin dragonets, and I've come to the conclusion it is possible to house them in a nano tank as long as they are given the right conditions.

Philosophy
I believe keeping a healthy, happy green mandarin goby in a ten gallon tank is possible. I also believe we will soon be seeing tank-raised and aquacultured green mandarins in the next ten years. Feeding issues will be a thing of the past, and farm-raised mandarins will eagerly accept frozen and processed foods. Nano tanks are very new to the saltwater scene, and fifteen years ago a marine aquarium under 55 gallons was absolutely unheard of. Thanks to new lighting technology and the Berlin method of natural filtration through live rock, smaller quantities of water are holding fish and corals aquarists never dreamed of keeping in 100+ gallon tanks.

Mandarins are some of the most popular, easily available, and cheapest fish on the saltwater market. They experience the greatest mortality rate of marine fish as well. Given these two facts, and given the nature of capitalism (let alone the evolutionary advancement of the marine and reef hobby), I believe we'll be hearing a lot more stories of mandarins eating frozen and pellet food and thriving in tanks once thought impossible to sustain them.

In fact, this is already happening. Many marine hobbyists who've done their homework have reported success in keeping mandarins in nanos, and several have even weaned them onto pellet food. Unfortunately, people are often afraid to admit their success on forums. As mentioned above, keeping mandarins in anything but the traditionally accepted housing--100 gallons, 100+ pounds of live rock, a 2-year old, "mature" tank--brings out the worst in some people. For whatever reason, they will not open their minds to even the idea of success.

Originally, I agreed with them. However, once I really delved into google and nano fish forums, I found many different people reporting the same success stories... a green mandarin eating bloodworms, a freshwater food (which I feed my discus); a green mandarin being supplied pods daily from a separate pod culture tank; a whole tank of mandarins eating Formula 1 pellets. They were always met with the same hostile or rude responses and arguments. Your fish will starve after 6 months. They cannot be kept in systems without an excessive colony of pods. Etc.

I am determined to try and keep a successful and healthy mandarin in my ten gallon. I have done my homework, and I hope you have too. Here are some more thoughts:

• I will do everything in my power to provide the mandarin with the nutrition and care it needs.
• I believe experimenting with pets is good, as long as the caregiver has done his homework.
• Fish are not people. Attaching human elements onto fish or any lower animal is a fallacy. I am not "torturing" a fish for selfish or aesthetic reasons; I am advancing the hobby by trying to do what others have successfully done before.
• If my experiment fails, I am prepared to "eat" the fish and all the expenses. I will return the mandarin to the LFS, and I will probably try again with another specimen. If I fail again, I will most likely give up; however, I will never condemn someone who tries the same thing.
• I will not know if things are going swimmingly until I reach the six month mark.

Background
The green mandarin, or Pterosynchiropus splendidus, is a member of the dragonet family. They are also known as psychedelic fish. Rarer specimens come in reds and there's even a spotted variety, but the average mandarin you'll see in fish stores is the green mandarin male. Males are selected over females because of their more impressive dorsal fin.

Mandarin gobies hail from the Philippines and the Melanesian islands. They are naturally found in reefs or coral rubble with rich sand beds, constantly on the hunt for small crustaceans.

Each specimen is wild caught and exported. Despite their popularity, they are not yet endangered--as shown by their rock bottom prices. Though a mated, healthy pair breeds and lays eggs often, cultivating the eggs and raising the fry has not yet been done successfully on the commercial market.

In the wild, mandarins can consume a vast number of copepods, amphipods, and other "pods" daily. They are extremely difficult to wean onto frozen or processed foods, and many mandarins will never accept anything but live pods. This is why they are considered expert level fish and are thought to best thrive in large, mature systems with copious live rock.

Though your odds of success go up if you introduce the fish into a large, established reef system, many still experience losses. The variety and stacking of live rock seems to be as critical as the amount. The level of nutrients in your tank is also important. Pods must be able to thrive if your mandarin is to thrive.

Because dragonets have metabolisms similar to humming birds, they are always consuming, but they only eat in small portions. Ergo, an inadequate tank can have its entire pod population decimated in a matter of days. Good conditions for your pod population to sustain itself is the number 1 way to successfully keep the mandarin goby.

The Plan
I will arrange my tank to accommodate copepods, the mandarin's main food source. Instead of a fuge or a sump I will culture the pods in a separate venue: several quart mason jars on the windowsill. I will inject the tank with fresh pods on a regular basis so the population will always stay at adequate levels.

The image to your left is a bottle of aquacultured copepods. Each bottle contains 1000 copepods of three different species. They are nutritionally dense and provide the essential fatty acids that brine and other food often given to mandarins do not. Also, if you're able to sustain a constant population, you'll not have to worry about getting your mandarin to eat frozen or processed foods ever again!

According to Dr. Adelaide Rhodes, the creator of Oceanpods, "It is difficult to believe that something so small could have such a significant impact on the nutritional value of fish, but a good analogy is the dependence of whales on krill. Krill are just another type of marine crustacean rich in essential fatty acids, and the preferred food of many species of whale, which filter the krill out of the water by pushing them through the fine mesh of baleen found inside their mouths. Without the krill, the whales would die. Think of the size of the whale compared to the krill and you can begin to see how significant Copepods can be in the marine food web." (Source link)

Please see Dr. Rhodes's site for more information about Oceanpods and how to begin your own culture.

My pod factory will consist of multiple quart jars, each containing a nontoxic plastic dish scrubber (the coarse type of sponge that looks like fishing net). Once the progenitor batch of pods multiply and the population takes off, I will split the culture to the second jar, and then the third, etc. I estimate in a month's time I will be able to lift a scrubber from one jar and shake out enough pods in various life stages to keep my main tank's population at sustainable levels. The decimated quart jar will then have enough time to rebuild its population while I pillage the remaining jars once or twice a week or as needed.

In addition to the copious pod population, I will attempt to wean the mandarin onto frozen mysis, and ultimately, Formula 1 or Marine Cuisine. I've read reports of an LFS worker in Australia having an 80% success rate with getting mandarins to accept prepared or frozen foods. He used freshly hatched brine shrimp and "gut loaded" them with bloodworms and other frozen and processed fare, and slowly he weaned the mandarins onto the regular foods.

Some Tricks
Many hobbyists over the years have discovered a few tricks to help get a mandarin eating or plump. I've outlined several of them below.

• Use a refugium.
• Create a "pod pile" of small chunks of live rock in a corner. Pile the rubble up so fish cannot enter and spray the area with minute bits of food to herd the pods into the safety area to feed and reproduce.
• Target feed blood or blackworms, mysis, or Marine Cuisine to a crevice in the live rock. It is believed fish have selective memories and return to a location that is known to hold food.
• Try feeding roe, or fish eggs. These can be obtained at Asian markets under the name of flying fish eggs. They look like the orange little balls on sushi rolls.
• Employ a mandarin diner. Though this looks good on paper, I'll be very interested to see if it does anything for a mandarin that doesn't eat prepared foods.
• Stock your tank with porous and gnarly live rock. More surface area the better, and place them so there are fish-free areas. By many reports, mandarin success has as much to do with the placement and type of live rock as it does with the volume.
• Employ non-combative tankmates that won't go after pods. According to several hobbyists, some mandarins have duplicated the behaviors of other fish. One was even reported to have imitated a crab and begun to consume baby brine shrimp in the water column.
• Style your tank around the needs of pods and mandarins.

Conclusion
I don't know if this will work. But I'm willing to risk a lot--the fish, as well as a fair chunk of money--because I believe there is no reason why this hypothesis will not hold water. Nothing tried, nothing gained, as I see it. I've put a lot of thought and time into this project, not to mention investment. I would love to see mandarinfish in smaller tanks because they so easily get lost in the huge systems. I've thought my way through every step of the way, and if I fail... well, I can't say that I haven't been warned.

Progress

5/03/05 Update. I've had the mandarin for one week now. As posted in my blog, he continues to graze on the live rock, sand, and glass, and he continues to snare a goody every 5-10 minutes. I've injected pods twice now into the main tank. I added a scrubber pad into my little HOB filter box. The idea of the scrubber in the filter is to spray the fresh pods into the filter box and let them trickle down into the main tank as they are attracted to light. Algae and detritus from the filter, in theory, should sustain a small fuge-like population in the box.

Now the bad news.

The mandarin is not as plump as I'd like him be. He has improved since purchase, but I can still make out the line in his abdomen. I fear I may have bought one too far gone. As I see amphipods on almost every patch of sand and rock I look closely on, and I can find copepods with a flashlight at night, losing him will not be for want of food.

I've been in touch with Dr. Rhodes and I have started my second culture jar. However, my first jar may have been contaminated. I introduced some algae into the jar, and it could have possibly fouled the water and stunted the culture. Today I removed most of the algae with a prong. I believe most of the pods are deep in the sponge and out of my view, so I will have to wait longer to see a population boom.

Lessons learned: Do not add algae. It can hold unconducive hitchhikers as well as pollute the culture. Also, wait until you are seeing large growth before adding the scrubber. The pods seem to disappear into the pad and it is hard to gauge when you're ready to split the culture.

5/05/05 Update. Moved the scrubber pad from the filter box to the pod pile to prevent a nitrate build-up. The pod pile is much larger and now offers much more protection for the pods. At night I see amphipods everywhere. I also added a large seashell with more scrubbing material wadded inside.

The mandarin is looking better, I'm happy to report.

Pod production in the jars is coming along nicely. I see thousand of tiny pods on the second culture jar, the one without the pad.

5/24/05 Update. I apologize for the lack of updates. My wife and I were gone for two weeks on our honeymoon and my brother was house and fish sitting.

The mandarin is still alive and more active than ever. I expected the pod population to be decimated when I got back, but on the contrary, it continues to boom. There are more than ever and they appear to keep multiplying. There is now a new species of pods, little black ones smaller than the clear amphipods and full grown copepods. They infest parts of the glass that has slimy green algae as well as the sand and many rock and shell surfaces.

I injected a new source of pods a few days ago. Unfortunately, they are so small it's very hard to tell if I'm injecting anything at all. I started a new culture jar with the decimated scrubber pad I used to "replenish" the main tank.

Here's some conjecture. Perhaps the cultures are not entirely necessary. I believe the scrubber pads and live rock rubble are the sole reason the population is not only keeping up with the mandarin but growing larger. However, I cannot safely conclude this because there hasn't been enough time to truly tell.

The mandarin's appearance remains skinny. I find this disturbing because the frequency of which he consumes pods has increased; he eats something every 2 or 3 minutes now. I don't know what this means, but I have some guesses. One, he may have been too far starved when I bought him. Two, his belly will come back slowly. Or three, he just appears this thin and it's nothing to worry about. After all, the only information I'm going on about their appearance has come from the same people who said this experiment could never be done.

For more recent updates, please see my mandarin fish updates page.