Re:90G set up for mandarin,seahorse,coral system etc?

Pete Giwojna

Dear Clintos:

Yes, sir, your post is certainly appropriate for this forum and I would be happy to discuss your proposed setup with you.

I absolutely love the psychedelic coloration and peaceful nature of Mandarin dragonets! There’s no disputing that they are gorgeous little fishes and make ideal tankmates for seahorses in the right type of setup. They are docile, slow-moving, passive fish that are beautifully marked and very deliberate feeders. And they are quite hardy fish providing they can be fed properly. They have a heavy slime coat that seems to make them quite resistant to protozoan parasites such as Cryptocaryon irritans.

But, as you know, in order to do well, mandarins need a large, well-established aquarium loaded with live rock or live rock rubble that’s teeming with copepods and amphipods. Mandrins must have continuous opportunities to graze on suitable live foods or they generally slowly waste away and starve to death. In the right system, they can thrive, and will often learn to take small pieces of frozen Mysis, but they do best in well-established reef systems or aquariums with at least 1 pound of live rock or LR rubble per gallon, a mature sand bed, and a refugium that can continually replenish the pod population in the tank. Those are typically the conditions that are necessary to assure they have adequate suitable live prey. It sounds like that is pretty much the type of system you have in mind, Clintos, so I think you’re on the right track, sir.

Mandarins are bottom feeders that normally do not take food from the water column, so select an aquarium with a large foot print that can accommodate plenty of live sand, small pieces of live rock, live rock rubble, and macroalgae. If you want to maintain more than one Mandrin, and keep a male/female in top condition, the larger the aquarium (and therefore the more extensive pod hunting ground the Mandarins will enjoy) the better. If you want to keep one or more seahorses as well as the Mandarins, look for aquarium that’s at least 20 inches tall.

I agree with your thinking regarding the sump-mounted MRC protein skimmer for this particular application, sir — I would omit the MRC in favor of an algae scrubber. As you said, you want to encourage an abundance of nutrients to support a thriving population of phytoplankton, which will in turn support abundant zooplankton and microfauna to establish the self-sustaining food web you hope to maintain. I would go with the algae scrubber and avoid using an ozonizer, skimmer, or ultraviolet sterilizer in your mandrin tank.

If you want to keep an assortment of seahorse-safe soft corals such as zoanthids, palythoas, Ricordea, gorgonians and such, that’s fine, but I would not keep any wrasse in your aquarium. The reason for this is that the wrasse are all active feeders and will take more than their share of the zooplankton, copepods, and amphipods you were hoping to cultivate in this aquarium system. That’s not what you want if you hope to create a self-sustaining food web, sir. The wrasse would outcompete the dragonets and/or seahorses for the precious live foods, and that’s something you must avoid if you will be keeping a pair of Mandarins in breeding condition.

I would definitely include a refugium in the design of your new aquarium system, Clintos. It’s generally not possible to create a self-sustaining ecosystem in a seahorse tank in which the natural reproduction of copepods and amphipods is enough to sustain these seahorses without the aid of one or more well-stocked refugia. Our galloping gourmets will usually deplete the pod population faster than it can replenish itself. If you have a large enough aquarium with lots of live rock and a well-established, heavy population of copepods and amphipods and other microfauna — the type of setup that would be good for Mandarin dragonets, for example — you might be able to pull it off..

But you will increase your chances of establishing a self-sustaining ecosystem dramatically if you also set up Gammarus amphipods, copepods, feeder shrimp, and other live foods species in a refugium that’s connected to the main tank. That way the Gammarus and copepods and other small crustaceans can build up a very large population well they are safely protected from any predators within the refuge, and some of them will be steadily released into the main tank to replenish the supply of live foods for your Mandrins and/or seahorses.

A refugium is simply a self-contained protected area, isolated from the main tank but sharing the same water supply, which provides many of the same benefits as a sump. A refugium can help newly added fish or invertebrates easily acclimate to a new tank. It can provide a safe haven for injured fish or corals to regenerate damaged tissue without the need for a separate quarantine tank. But perhaps its main benefit for the seahorse keeper is provide a protected area where macroalgae can be grown and small live prey items (copepods, amphipods, Caprellids, etc.) that will eventually become a food source for the inhabitants of the main portion of the tank can be cultured safely, allowing their population to build up undisturbed.

For instance, Charles Delbeek likes to use colonial shrimp species in the refugium for his seahorse tank, where the regular reproduction of these hermaphroditic crustaceans will provide a continuous supply of nutritious nauplii for his ponies: "There is a method that can be used to offer an occasional supply of live food for your sea horses. By setting up a separate system housing several species of shrimp such as the common cleaner shrimp (Lysmata amboinensis), peppermint shrimp (Lysmata amboinensis), or Rhynchocinetes uritai or R. durbanensis, you can get a fairly regular supply of live shrimp larvae. These species are best to use since they can live in large groups and spawn on a regular basis. Such a system is commonly called a refugium. A refugium is a small (10-20 gallon) aquarium that contains live sand, live rock and/or macroalgae such as Caulerpa or Gracilaria. It is plumbed such that water from your main system is pumped to the refugium and then returns via an overflow to the main tank. Some of the pods and larval crustaceans will then be carried from the refugium into the sea horse tank in the water that overflows from the refuge. For this type of arrangement to work, the refugium must be slightly higher than the main tank. Shrimp are added to the refugium and within a few months they should start spawning and hatching eggs every few weeks. The larvae are then carried back to the main tank by the overflow, where they become a food source for your sea horses. Of course other life will also thrive in the refugium and it is not unusual for copepods, mysis and crab larvae to also be produced on a regular basis. The key to the refugium is to keep predators out of the system so that the smaller micro-crustacean population can thrive. You would need a fairly large and productive refugium to produce enough food to maintain even a pair of sea horses, so at best, a typical refugium can provide a nice source of supplemental live food; the basic daily diet still needs to be provided by you in the form of the frozen foods mentioned above." (Delbeek, November 2001, "Horse Forum," FAMA magazine).

I would set up one or more refuges like the ones Delbeek prefers for your Mandrin aquarium system, Clintos. Concentrate on populating your main tank with a dense population of assorted copepods and amphipods (Gammarus and Caprella species) and make sure the aquarium is very well-established with a booming population of pods, zooplankton, and other microfauna before you introduce the Mandarins. Try your luck with a pair of Mandarins first (one male and one female only — otherwise they will fight viciously among themselves), and if they do well, then you might consider adding one or more seahorses to the system. But if your primary goal is to keep a pair of Mandarins in breeding condition, you may want to omit the seahorses since they will be direct competitors for the live food with the Dragonets.

Best of luck with your most interesting project, sir — it should make a fascinating experiment and you’ll learn a great deal in the process whether or not it is as successful in maintaining a self-sustaining food web as you had hoped and envisioned. Please keep us posted when you get your new aquarium system up and running

Pete Giwojna

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