a newHarlequin future for the keeping and breeding Oxymonacanthus longirostris, a spectacular and challenging species Story and photos by Matt Pedersen TK 64 CORAL THET DAZZLING APPEARANCE OF THE HarlequinH Filefish, a flamboyant little beautyb with beaked snout and promi- Filefishnentn Swiss-watch eyes, represents the veryv reason so many of us are drawn to marinemarine aquariums. When in good health and fullfull ccoloration,ol it is an arresting species and undeniably seductive for fishkeepers. Common in the wild and found through- out the sprawling Indo-Pacific, from East Africa to Okinawa and Samoa, Oxymonacanthus lon- girostris is imported and offered for sale under a variety of common names, most often the Orangespotted Filefish (a common name also routinely applied to the west Atlantic species Cantherhines pullus), but also the Longnose File- fish or, in Australia, the Beaked Leatherjacket. Harlequin Filefish are typically offered at very affordable prices that often entice an uniniti- ated aquarist to make an impulse purchase. Only later does the hobbyist learn that the Harlequin Filefish is an obligate corallivore that experts say is “rarely alive for more than a week in captivity” and is “doomed to die,” a fish “best left in the ocean.” The pervasive infor- mation available suggests that this fish simply cannot be kept alive without live corals to feed on. Those who attempt to keep this species risk the condemnation of their fel- low aquarists, who often sug- gest returning the fish to the shop that sold it before it dies. What we might not consider is that this advice is often coming from people who have never attempted to keep the species— Large image: Trio of healthy Harlequin Filefish broodstock, male at center, in the author’s nano-reef. Inset: Female in good condition. TK CORAL 65 Group of newly imported Oxymonacanthus longirostris being drip acclimated in a 5-gallon bucket. they are simply repeating what they’ve been told. This it’s time to rethink our stance on this remarkable fish. notion, which is decades old, is so firmly entrenched in Experienced aquarists can master this species, but it’s hobby literature that most responsible aquarists never not easy. I must emphasize that wild-caught specimens question it, and choose to admire this species in pictures are absolutely not for beginners, or even hobbyists with or through the lens of a dive mask. a couple of years of experience. Keeping wild-caught Harlequin Filefish should only be attempted after care- BREAKTHROUGH EXPERIENCES ful deliberation and preparation by dedicated, advanced While that information may have been completely valid hobbyists. Even then, failure (death of a fish) is a pos- and accurate 20 years ago, it isn’t today. Inspired by the sibility that must be accepted before attempting to main- pioneering work of Iris Bönig, who in 2007 became the tain this species. first person to spawn and successfully rear the Bristletail How did the Harlequin Filefish go from doomed to Filefish (Acreichthys tomentosus), I set out to follow her viable? Advancements in the chain of custody from col- lead. I was unable to find Bristletail Filefish locally, but lector to home aquarist mean that sensitive fish arrive instead serendipitously encountered Harlequin Filefish, in better shape now than they did in past decades. The which I reluctantly purchased, assuming failure was like- reduction of drug-caught specimens in the supply chain ly. To my own surprise, in a little over a year I’ve attempt- has also lowered the incidence of “mystery deaths,” espe- ed to keep 17 wild-caught Harlequin Filefish—and suc- cially those that occur in the short term. A better under- cessfully established 12. While I’m not the first to spawn standing of overall marine fish nutrition has resulted in this species in captivity (a single anonymous spawning the availability of far more diverse and nutritious foods report was submitted to the Breeder’s Registry in 1994), to offer our fishes. Equipment and husbandry develop- I believe I’m the first person to successfully spawn and ments, spurred by the boom in reefkeeping in the last rear this species in captivity (and in completely closed two decades, have given us the ability to provide more culture as well), producing the world’s first captive-bred stable, more pristine environments. Improved knowl- Harlequin Filefish. Based on what I’ve learned, I believe edge of marine-fish social structures and behaviors have 66 CORAL helped, too. The Internet has also brought aquarists to- and pellet foods, as well as frozen blended diets, enriched gether to share personal experiences and offer creative frozen brine shrimp, Mysis shrimp, minced squid, and solutions to urgent problems. more. These fish simply won’t thrive without multiple feedings every day. DIETARY MYTHS Harlequin Filefish are somewhat reef safe. A few To reassess the Harlequin Filefish, we must address the aquarists have successfully maintained these fish in large core belief that they will die without live coral flesh in reef aquariums of 200 gallons or more (757+ L) that are their diet, specifically the polyps of small-polyp stony filled with SPS corals. They note no visible damage from (SPS) corals such as Acropora, Montipora, and Pocillipora the filefish feeding on the corals, but some corals cease species. This is simply not true. I am aware of several to extend their polyps during the daylight hours. aquarists who have documented captive lifespans in the For the rest of us with smaller reefs, consider that range of three to five years, feeding nothing but prepared a well-fed filefish is less likely to antagonize the corals. foods. The fact that this species has been brought into The Harlequins kept in my SPS tank ignore Montipora daily spawning condition with only prepared foods fur- capricornis, but do nibble on M. digitata and Seriatopora ther disproves the hypothesis that there is some critical hystrix that continue to grow but no longer extend their nutritional element found only in live corals. My first polyps when the lights are on. Other aquarists have had captive-bred juveniles have been reared exclusively on problems with LPS corals such as Acanthastreas. You rotifers and baby brine shrimp, later weaned onto pellet should be prepared to address the incompatibilities that and flake foods. These babies even went so far as to show may occur between this fish and your corals. no interest in live coral when it was offered, While circumstances preferring the prepared foods. It is fair to say have improved for this that we do not know the true nutritional species as a wild-caught requirements of Harlequin Filefish—indeed, fish, they are still one of does anyone know the nutritional profile of the most difficult marine coral flesh? In the absence of that informa- tion, I have simply offered a widely varied Left: Moderately emaciated omnivorous diet based on the rudimentary male, showing sunken belly supposition that coral consists of both “ani- and nape. mal flesh” (the coral polyp itself) and “al- Below: Plump male after gae” (the zooxanthellae contained within). months of transition to prepared aquarium foods. LIFE IN CAPTIVITY It’s important to know that this spe- cies is best kept singly or in hetero- sexual pairs in a tank at least 10–25 gallons (38–95 L) in size. I have kept a trio (one male, two females) and pairs of females, but I can almost guarantee that two males will not coexist peacefully in the average hobbyist aquarium. Fortunately, sexing Harlequin Filefish is easy. The most pronounced sexual differences are in the ventral flap or pelvic rudiment. In males, the ventral flap is bright orange-red, bor- dered above by a thick band of black containing a few rows of fine blue- white spots. In females, the ventral flap is often black but at times may be a dirty orange. The prominent black border is absent in females, and there will be few fine white spots. Being active grazers, Filefish re- quire several feedings per day. My fish feed on multiple types of flake CORAL 67 Left: Do-it-yourself filefish feeding sticks: frozen Ocean Nutrition Formula One marine protein and algae cubes, thawed and pressed onto dead branches of Acropora coral rubble. Opposite page: Weaning a filefish onto homemade feeding sticks. Inset: A newly arrived filefish eats coral polyps on a Bali Green Slimer, Acropora yongei. new fish. Individual specimens establish themselves at different paces, and shared quarters can inhibit progress. A male, for example, may dominate a female before she has a chance to start eating and renourishing herself. For each fish, provide a 10-gallon (38-L) aquarium and all the basics—heater, simple light, filtration, and aeration. (I use Duetto 100 Internal power filters.) A Seachem Ammonia Alert Badge will help you quickly de- tect deteriorating water quality. You should pre-establish the filter media in your main aquarium sump or filter, and then move it to the quarantine tank when needed. Leave the tank bottom bare for easy cleanup of un- eaten food. Provide hiding places for the fish, but under fish to bring into captivity. They share traits with many no circumstances should you include anything resem- other fish typically considered for-experts-only, such as bling coral or coral skeletons. I’ve watched Harlequin Mandarin Dragonettes (Synchiropus sp.) and wild-caught Filefish nip at dead coral skeletons for hours on end in Seahorses (Hippocampus sp.). One or two mistakes are all dealer’s tanks, desperately trying to feed on something it takes to turn possible success into guaranteed failure. that simply isn’t there. We’ll take that strong instinctive There are several key considerations necessary to estab- feeding response and use it to our advantage.