A couple of weeks back while looking around an aquarium store in the Midlands I was a little disturbed to come across a pair of Oxymonacanthus longirostris, known variously as the Longnosed Filefish or Orangespotted Filefish. This gorgeous fish, with its unusual patterning of orange spots on a blue background, is an obligate corallivore specialising in Acropora polyps, resulting in an extremely poor record for survival in the aquarium.
My first reaction on seeing this notoriously difficult fish for sale was one of horror, but since then I’ve talked to a couple of wholesalers and had a bit of a rethink about the situation. This doesn’t mean that I’m going to encourage any one to purchase one of these fishes, in fact quite the opposite, but It makes an interesting subject to discuss in this month’s column.
First off, a bit more information about this fish (courtesy of Fish Base):
A member of the family Monacanthidae or Filefishes, this is a reef-associated fish occurring in clear lagoons and seaward reefs with a depth range of around 0.5 metres to 30 m. They tend to be found in pairs or small groups nesting near the bases of dead corals, often on clumps of algae. They grow to a maximum total length of 12 centimetres and appear to be monogamous. Males may be identified by having bristles on the caudal peduncle that are longer than those on the body. Reports from the field indicate that this fish feeds exclusively on Acropora polyps with feeding taking place throughout the day becoming less towards the evening. Further reports from the Marshall Islands mention the following corals as being eaten: Acropora acuminata, Acropora nasuta, Acropora valida, Heliopora coerulea, and Porites cylindrica.
They have a distribution in the Indo-Pacific from East Africa, south to Maputo, Mozambique, east to Samoa, north to Ryukyu Islands, south to the southern Great Barrier Reef, New Caledonia, and Tonga. This species is replaced by Oxymonacanthus halli in the Red Sea.
Note: This fish is also known as the Harlequin filefish in the US where Orangespotted filefish can be used as the common name for an entirely different species, Cantherhines pullus, a 20 cm long Atlantic filefish with a distribution mainly in the western Atlantic including “Floribbean waters”.
I’d suggest the use of Longnosed filefish as a more universally accepted common name.
Don’t you just love the confusion caused by common names…
A Look at the Hobby Literature.
Reviewing the hobby literature on this species you get an overwhelming reaction of not suitable for captivity – best left in the ocean.
John Tullock, in Natural Reef Aquariums (1997 and still an informative book 10 years on) puts this fish into a category defined as follows: Special requirements for this species, usually dietary needs, cannot be met by the home aquarist. Appropriate conditions for this species are not yet defined. He then goes on to include it (along with its relative O. halli) in a table of Fishes with Special Dietary Needs, and also in a table of Marine Fish Species Not Successfully Maintained by Public Aquariums.
Writing in the Conscientious Marine Aquarist (first published 1998 but still a useful book) Bob Fenner says, “Leave it in the ocean unless you are farming corals. Otherwise it will starve to death in your tank”, before going on to say that he thinks all members of the genus Oxymonacanthus are corallivorous and as such should be avoided.
The Complete Book of the Marine Aquarium (2002) Vincent Hargreaves says of aquarium suitability, “This is not an easy fish to keep in an aquarium for any length of time since its main diet is coral polyps particularly those of the Acropora spp.”
Dr Elizabeth Wood, in the Responsible Marine Aquarist (2003) makes the point that as long-nosed filefish feed exclusively on Acropora and seldom survive for long in captivity, that they should be left on the reef to avoid unnecessary wastage. In the reference table at the back of this book it’s classified as “Virtually impossible to maintain”.
In Advanced Aquarium Techniques by Jay Hemdal (2006), a book written mainly from the perspective of a public aquarium aquarist, this fish is included in the table headed: Fish That Rarely Survive Past the First Year Mark in Closed System Aquariums.
I’ll leave the last word from the hobby literature to my buddy Scott Michael. In Reef Aquarium Fishes (Pocket Expert 2006), Scott says, ”Some reef keepers have successfully housed this species in a tank with numerous SPS coral colonies. If there are enough corals to feed on and only one or a pair of these fish are kept, they may not damage any one colony enough to cause its demise. That said O. longirostris is best avoided by most aquarists. (One in hundreds may accept substitute foods, but most specimens waste away and die.)”
Previous UK Aquarist Query.
In, I think, 2004 I had a PFK reader query about the Orangespotted Filefish, I responded with the article: Catering For Picky Feeders On The Reef, which I’m reproducing here in part.
So here’s the letter from reader Rob Burns who started my interest in these fishes.
I was a very enthusiastic marine aquarist for several years until about 10 years ago when a combination of children and setting up a business meant I had to give up the hobby.
I am now interested in getting back into the (much changed) hobby as circumstances now allow for the time and dedication required.
I would really like to set up a ‘specialist’ tank to keep just one species, the Long Nosed Filefish, Oxymonacanthus longirostris. I am aware that these are very difficult to keep although I did achieve some modest success all those years ago in a mixed but ‘quiet’ tank. I had thought about setting up a largish tank with predominantly Acropora species, which I believe, is the natural diet of this species in the wild and a small group of these fishes.
My question is whether you think this would be possible/advisable; whether it would still be possible to import this species for such a set up and whether with care and attention to other dietary needs it might succeed? I have always been fascinated by this particular fish and would derive a great amount of pleasure from being able to keep them.
My first thought was “Whoa! Forget it!”, but after I’d reflected on the idea for a while I changed my mind. I’m generally against stocking hard to keep species in shops, but if an aquarist is after something in particular and demonstrates knowledge of the animal, I’m usually happy to order one in.
I prefer to discourage the average fishkeeper from buying these more specialist creatures. The thing is, we are now keeping animals in our tanks that a few years ago we wouldn’t have thought possible; if responsible aquarists are prepared to work at problem animals then maybe, in years to come, we’ll be able to successfully keeping even more species.
As you’ve mentioned, the problem with this stunningly beautiful fish is, with its diet of Acropora polyps, this fish is an obligatory corallivore. In his book, Marine Fishes, Scott Michael mentions that it can be occasionally persuaded into eating live brine shrimp, though this will rarely fulfill its nutritional requirements.
I think you’re on the right track, setting up an Acropora tank, but I’d suggest going one step further and incorporate an Acropora refugium into your system. Acropora are very hardy and easy to grow given the right conditions, so by farming them in the refugium (where they’re safe from predation) you could then rotate them between the display tank and the refugium. By rotating them back to the refugium they’d have an opportunity to recover and grow.
If you want to try supplementary feeding make sure any live food is enriched with either a product such as Kent’s Zoecon or phytoplankton. If the fish are reluctant to take food from the water column you might like to try pushing something like shrimp into the surface of a coral skeleton or rock to simulate polyp flesh.
Incidentally, I’ve also come across a report of Oxymonacanthus longirostris spawning in captivity, placing adhesive eggs on to the glass of the aquarium
I’m afraid that although I’ve been writing this answer up in an encouraging manner saying, yes its doable for someone prepared to put in the money, time and effort, its unlikely that you’ll be able to get hold of the fish. A couple of years ago the main marine wholesalers in the UK, TMC and KKC, agreed not to import this fish on the moral grounds of it being to difficult to care for. Also the key to success with this fish would appear to be to obtain good quality stock, which is very much dependant on the standard of the holding facility that they are imported from.
Back to Today …
As I said at the beginning I‘ve again talked to the main wholesalers about this fish.
The story is, that having located a good reliable source for these fishes, where the fish are looked after and it’s ensured that they’re feeding, TMC are bringing in a small quantity each year. They are being collected to order and only going out to stores that know what they’re doing. I’m also told that they’re aware of fish that have done well over time. The rationale seems to be that as these fish are feeding well and surviving import that they should be OK to sell. This is in contrast to the situation a number of years back when far more of these fishes were brought into the country only to die within weeks of importation. Further, that by making small numbers available, it avoids the unnecessary wastage that occurs when fish are brought in through console from sources – this is where the retailer picks their fish off of an import list and the fish are delivered direct to the store.
(Console, or consolidation, can work well in the hands of knowledgeable retailers who go to the trouble of quarantining their imported fish before putting them on sale but, in the case of the numerous outlets where these fish go straight into the sales tanks on delivery, it can be a recipe for disaster.)
OK, fair enough so far, but I’m still skeptical on two points – that the fishes do go to retailers who really know what they are doing, and that they are exhibiting long term health. Think back to Scott’s comment about the number of longnosed filefishes that die for every one that survives.
There’s not much I can to about the first point but I‘m interested in exploring the second one.
Instead of just taking a prohibitive view on the grounds of the literature stated above it might well be worth assessing the survivability of the longnosed filefish in today’s reef aquarium Unfortunately this may prove difficult to do as we’ll be relying on anecdotal evidence from aquarists of widely varying experience and ability, not to mention the veracity of said evidence as there can be something of a competitive aspect to maintaining difficult animals that may lead some aquarists to, shall we say, exaggerate their successes.
So, Can the Longnosed Filefish Be Successfully Kept?
Although a fish may be feeding on what would appear to be an adequate diet this does not mean that it’s receiving adequate or appropriate nutrition. The references to these fish feeding on Artemia, or brine shrimp, is a little worrying when you consider what a poor source of nutrition these are if they’ve not been enriched.
One aquarist may view a fish that has survived for some time as a success, whereas another aquarist’s interpretation may be that it was just a stronger fish that took longer to starve to death than …
The fact that there are reports of this fish surviving in a few aquariums may indicate that its nutritional requirements can be met in today’s reef where there are both more corals and more incidental animals, critters, available as a food source than in the more sterile aquaria of ten years ago.
Kept only in ones or twos with sufficient stony corals to spread out the damage and so keep pace with the feeding demand there seems to be little reason for them not to survive. To achieve this you’d need a mature reef with conditions optimized for coral growth, the sort of reef that can be regularly harvested to produce frags would seem ideal.
So, although it would seem reasonable to be able to successfully maintain longnosed filefishes in captivity, it seems self evident that the aquarist who’d like to keep them will need to be experienced enough to provide the conditions required for SPS growth yet at the same time be sympathetic towards the idea of growing corals as food.
If you’ve kept these fishes, successfully or not, it would be interesting to hear from you so I can put together a more complete picture of their survival in captivity.
Standard admonishment: Always research the requirements of any animal you’re interested in purchasing. This doesn’t just mean ask the guy in your local fish shop – the retailer won’t always know and unfortunately I hear many reports of bad advice being given …
Best advice can often come from someone with experience of keeping your chosen beast but even that’s not always going to be correct – think about what you’re told.
You have to take responsibility for the fish or invertebrates you buy, if you don’t feel confidant that you can fulfill its needs don’t buy it!
Any questions or comments, please feel free to get in touch with me.