So many fish and so little space.” That is the mantra I hear from so many of my “fish geek” buddies. Reef fish communities are so diverse, and many of these beautiful and fascinating species are available to hobbyists – it simply boggles the mind! Many people concentrate on acquiring those fish that are the most aesthetically appealing. Others are more likely to select a species because it exhibits interesting mannerisms that can provide hours of enjoyment. There is a fish that falls into this latter category that is a blast to watch, but it can also cause the aquarist to pull his or her hair out if it is kept in the wrong living situation. This fish is the dragon or rockmover wrasse (Novaculichthys taeniourus). It is readily available to aquarists, and many neophytes have purchased the docile, dragonlike youngsters, only to regret it bigtime after their fish put on some body mass.
The dragon wrasse has both good and bad attributes. By the time you finish this article, you may be ready to put a dragon in your tank, or you may decide this fish is not going to work for you. In either case, I hope you will appreciate it for the interesting and resourceful fish that it is.
The dragon wrasse is a member of the family Labridae and the subfamily Xyrichtyinae (formerly Hemipteronotinae). Some other genera in this subfamily include Ammolabrus, Cymolutes, Iniistius, Novaculoides and Xyrichtys. The dragon genus, Novaculichthys, contains two species: the dragon wrasse (N. taeniourus) and seagrass razorfish (N. macrolepidotus).
A Dragon’s Life
The dragon wrasse is somewhat of a cosmopolitan of the Indo-Pacific. It is known to occur from the east coast of Africa and the Red Sea all the way to the Hawaiian Islands (where many are collected) and the coast of Panama (including the islands off the west coast of the Americas) and the Gulf of California. It occurs as far north as the southern islands of Japan (the Ryukus) to Lord Howe Island and New South Wales, Australia, in the south.
One finds the dragon wrasse on both coral and rocky reefs. It is found in protected lagoons, near the edges of reef faces over sand and rubble bottoms, and on sand and rubble slopes. Over parts of its range, the juveniles also live in seagrass beds. The dragon wrasse tends to be a resident of relatively shallow depths, having been recorded from depths of less than 1 foot to 70 feet.
Both juveniles and adult N. taeniourus are solitary fish. When it comes to its social life, data is lacking, but it is probably similar to other members of the razorfish group; in this group, males defend a larger territory that contains the smaller territories or home ranges of a group of female dragon wrasse mates.
The spawning behavior of dragon wrasses has been observed in the wild. Males and females are similar in coloration and nearly equal in size. They court for five to 10 minutes; during such sessions, the male, with his fins spread, will circle a prospective female. The male then rises into the water column, followed by the female until they are side-by-side. They continue to rise slowly and release their gametes into the water column at the top of this ascent.
The spherical eggs are 0.59 millimeters in diameter and contain an oil droplet that makes them buoyant (they are pelagic). The wide geographical distribution of the dragon wrasse may be a function of the duration of the larval phase. The larvae float about in the pelagic zone and are at the mercy of ocean currents for about 75 days. This is a particularly long larval phase for a wrasse.
The juveniles engage in what would best be considered a masquerade – they impersonate drifting pieces of algae. The young fish is flattened laterally, having long pelvic fins and elongate dorsal fin filaments. The fin rays are dark in color, while the membrane is clear, giving the body an even more frilly or filamented appearance. Along with the variegated white, black and reddish-brown or dark green coloration, these embellishments facilitate its likeness to plant material. They not only look like plants, they also behave in a way that enhances this resemblance. They undulate, drift and dip as they move just over the seafloor. It is thought that by resembling botanical flotsam, the juvenile dragon wrasse is less likely to attract the attention of roving piscivores.
If a predator does approach, the dragon wrasse exhibits another interesting behavioral trait. It will dive head-first into the soft sand. Now you see it, now you don’t! Not only does the dragon wrasse disappear under the sand, the little fish can undulate its body when buried to actually relocate when submerged. In this way, it can pop out in another location, just in case the predator remains in the area, waiting for the dragon wrasse to re-emerge.
As the dragon wrasse grows, its colors and fin appendages are transformed (the juveniles were once thought to be a distinct species, which was referred to as Novaculichthys bifer). The filaments shrink, and the mottling becomes more of an organized honeycomb pattern of gray spots on a dark body. The head turns gray overall, and the tail becomes white with a black band at the rear edge. This fish is a medium-sized wrasse, reaching a maximum length of around 10.5 inches.
Rock and Roll
If you look at the lifestyle of the dragon wrasse, it should be obvious to the potential dragonkeeper why it is such an interesting fish to keep. It is an extremely resourceful and smart fish. As mentioned in the introduction, one of the common names for this fish is rockmover wrasse. It gets this moniker because of its fascinating habit of taking bits of rubble, rocks and coral fragments into its mouth and tossing them to one side as it hunts for concealed invertebrates and diminutive fish. The dragon will sometimes lift and move pieces of coralline debris that weigh as much as the fish itself does.
The dragon wrasse does not only move rubble and coral fragments to find food, but it will also construct sleeping mounds by piling up heaps of benthic debris. In the wild, these mounds consist of between four and 70 pieces of coral fragments. These are piled on mounds of sand. Just before sunset, the wrasse dives into the sand under its sleeping mound, which apparently makes it less vulnerable to nocturnal predators or may make the potential sleeping site less attractive to other burrowing wrasse species that are more likely to “bed down” in areas that lack rubble.
Because it is so effective at disturbing the substrate and exposing organisms hiding beneath, it is an attractive fish for many opportunistic fish to follow. For example, young bluefin jacks (Caranx melampygus) regularly escort hunting dragon wrasses off the island of Aldabra. It might also be followed by other wrasses and spine cheeks (Scolopsis spp.).
How to Train your Dragon
The young dragon wrasse can be housed in a tank as small as 20 gallons, while an adult will need an aquarium of at least 75 gallons (preferably larger). It is an active fish that will appreciate some room to move. It is also essential that the aquarium has a bed of fine sand that is unobstructed and free of major decorations. The depth of the sand should be at least 4 inches. To make things more interesting for your dragon wrasse (and for you), add some chunks of coral rubble or shells, so you can watch the fish work its rock-moving magic. Make sure that the larger pieces of decor are on the glass bottom of the tank (not just on the sandbed surface) so that if the wrasse buries, it does not excavate under the rockwork and get crushed as a result of a cave-in. Remember that it will hide under the sand at night and if it feels threatened. Resist the temptation to dig the fish out during acclimation. It may take it a while to adjust, but eventually it will begin coming out and staying out when the lights are on.
The most sensitive period for your dragon is when a juvenile is first introduced to the aquarium. In order to acclimate, it should not be bullied. It is not uncommon for the newly acquired dragon “pup” to be a bit reluctant about accepting normal aquarium fare. Yet in time, it will typically ingest finely grated seafood (take frozen seafood and use a cheese grater to get the particle size that best suits your fish), frozen mysids (whole adult mysids may be difficult for the smaller juveniles to ingest) and frozen preparations for carnivores. If your dragon is harassed by prior residents, it may hide incessantly under the sand and reject food.
Adults, on the other hand, tend not to be persnickety. They will eat any meaty food added to the aquarium – make sure you vary the diet as much as possible to keep your N. taeniourus healthy. If you have placed rubble on the bottom of your tank, you may want to add a handful of live ghost shrimp or fiddler crabs. In the wild, dragon wrasses will tear up the seafloor to get at these delectable crustaceans. You can also hide some pieces of table shrimp under the rubble and see if your dragon wrasse can find them.
The dragon wrasse’s habit of flipping over benthic bits and pieces is one thing that makes this animal so interesting in the home aquarium; however, for those who want to keep sessile invertebrates, this habit can be bad for your corals and your constitution. Novaculichthys taeniourus will take live coral fragments in its mouth and chuck them off reef structures. Larger specimens have even been known to lift and overturn fungiid corals (mushroom or plate corals). Being thrown about can cause mechanical damage to a coral’s polyps, as well as provide more work for the aquarist (i.e., regularly replacing and placing corals upright). If you are tempted to add a dragon wrasse to your reef aquarium, you will want to make sure any coral colony that is small enough for it to lift has been attached to the reef structure.
Another characteristic that you need to take into consideration before adding N. taeniourus to an invertebrate aquarium is its diet. This fish looks at much of the invertebrate world as a living buffet. The dragon will not eat sessile species, such as sponges, tunicates and corals, but anything that moves is a potential target. It will consume bivalves, snails, various crustaceans (including crabs and shrimp), sea urchins and brittle stars. Be aware that cleaning shrimp are not spared just because they may pick the occasional parasite from their fish tankmates. While a dragon wrasse’s potential to do harm to ornamental inverts is a function of its size (the larger they get, the more lethal they become), sooner or later, the dragon’s lair will probably be devoid of any invertebrates besides corals.
Not only are motile invertebrates in danger, subadult and adult dragons will also capture and eat any fish small enough to subdue and swallow. This includes perchlets, small anthias, gobies, firefishes, dartfishes, dragonets and blennies. This is one of a few predators that will even eat poison fang blennies (Meiacanthus spp.). They will bite and dispatch these fish before tearing them into bite-sized morsels. There are few places to hide when it comes to the wily dragon wrasse – it will deconstruct the refuges of fish that shelter under rocks and rubble.
So, don’t keep motile invertebrates and small, bite-sized fish in an aquarium with a dragon wrasse – which is a pretty simple rule to follow. However, there are other things you need to consider when it comes to the dragon’s piscine tankmates. Large subadults and adults can get mean in the confines of a glass box. As with other potential aggressors, this sociopathic behavior tends to occur most when the dragon has been in its lair for a while. After becoming fully acclimated, it starts looking at its aquarium as its territory. Any new fish added after it will be seen as an intruder, and the N. taeniourus may attempt to evict it. The problem: where do interlopers go in an aquarium that has a footprint of 1,700 square inches? For this reason, the dragon wrasse must always be the last fish placed in the aquarium and should only be housed with other boorish species that can hold their own with this beast. A list of potential tankmates includes larger squirrel-fishes (e.g., Holocentrus spp.), groupers, Labracinus dottybacks, Paracirrhites hawkfishes, Holacanthus angelfishes, snappers, large grunts, large hogfishes (Bodianus spp.) and most triggerfishes. The dragon wrasse has some nice-sized canines that can do some serious damage.
One thing you need to remember before filling your tank with aggressive fish is that the juvenile dragon wrasse is not likely to acclimate if it is harried by its neighbors. So while the fledgling N. taeniourus does best in a more peaceable community (at least in tanks of more limited dimensions), as it grows in size, so does its attitude and desire to cause problems with tankmates. If you are as enthralled with the behavior of this fish as I am, you may just want to raise a juvenile to an adult in a live-rock-only tank of 75 gallons or larger. The fish should be able to live out its whole life in a tank of this size and will become a fun and fascinating pet. While the dragon wrasse is certainly not well-suited to peaceful fish community aquariums or most reef tanks, its appearance and behavior are interesting enough that it should be considered for a more aggressive fish-only tank or a larger species tank. Happy fish-watching!