#misunderstood fish

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Some of the most iconic fishes on the coral reef are the marine angelfishes or pomacanthids, fishes that are reef-associated and strictly marine by nature, and completely unrelated to the popular freshwater cichlids also known as angelfishes. It is unsurprising, then, that aquarists have often expressed an interest in keeping saltwater angelfishes in expensive aquarium aquascapes featuring living corals and clams. Opinions about this range from those alarmists who say it is impossible, to those boasting that they have in fact done so without consequences. The concensus of opinion would have it that the endeavor is risky: it does indeed that some individuals within certain species, will take bites out of corals or clams, whereas others would not. This does not help the aquarists to choose a 'reef safe' individual fish, of course, but it does explain the variance in the anecdotes about angelfishes in reefkeeping.

None of the angelfishes is a specialised corallivore, or coral eater. This does not mean that they are physically or physiologically incapable of eating coral tissues, and in fact it is verified that some large angelfish species do, in fact, consume corals and anemones as items within broader diets, in the wild. For example pomacanthids are adapted to accessing prey that are in and around crevices, and pomacanthids are known to extract and consume live sea anemones. It is unsurprising that such broad spectrum feeders will behave similarly when they are in captivity. Early on in their evolutionary history, pomacanthids evolved the ability to close their jaws whilst they are extended, as during normal suction feeding. This ability to bite down whilst reaching to items attached to the seabed, allows them to grip and tug efficiently at tough masses of sponges and colonial tunicates - items that are much more difficult for other fishes to eat. They are specialised in a very different way to the butterflyfishes, which also consume attached animals, but trend towards the evolution of corallivory. The difference is that between a horse and a deer on land, or maybe that between a white and a black rhinoceros. Angelfishes partition resources with butterflyfishes, because they eat in different ways; angelfishes as a whole are not inclined to be selective feeders, and they chomp indelicately at masses of tough, living tissues, whilst the butterflyfishes instead tend to nibble more selectively.

Surrogate behavior is thought to explain why individual angelfish start to bite corals and clams mantles in the aquarium. In the science of behavior, surrogate behaviors are those that arise when a natural instinct cannot find natural expressions; so that in humans, for example, shopping becomes a surrogate for gathering foods. Angelfishes in the wild, are surrounded by spongal growth and tunicate colonies, and the behavior of feeding on then consumes a great amount of their time. Not surprisingly a frustrated angelfish will not improbably begin to bite on surrogate items, in the same way, if the normal targets of such behaviors are not present. That some fish do this more predictably than others in the same species, is presumably due to personality traits such as curiousness and a tendency to act upon natural impulses - otherwise the unpredictability of coral and clam biting by angelfishes is inexplicable. The phenomenon is noted even in an unusually specialised non-coral eater (ie. Pygoplites) as well as the more typical, broad spectrum feeders.

The diets of all angelfish are not equally well known, but as a clade, their anatomy is well studied as regards eating and digestion. Individual variation in behavior must be borne in mind, alongside the fact that some angelfish species actually have are faculative coral eaters in the wild. Most worry is expressed over the dwarf angelfishes - classically the genus Centropyge, but now three different genera - which older books as late as the 1980s, used to categorise as 'reef safe' - a meaningless term that ignores the realities of ecology, but one broadly defined as something like 'compatible with and harmless to living corals, and all (or almost all) sessile invertebrates'. Many dwarf angelfishes do, in fact, have diets rich in sessile, attached animals, and such items can even predominate in their diets on the reef.

The confusion perhaps arose from comparative anatomy: Centropyge teeth resemble those of blennies, another clade that consumes much algae, but cannot be regarded as strictly herbivorous, on the whole. The same older books used to tell the reader that blennies were reef safe, without reservation: in reality many eat coral polyps as natural parts of their diet, and one genus eats only stony coral, despite not having obvious craniodental adaptations to coral eating. The comb-like teeth of blennies, and of dwarf angelfishes, are actually efficient 'multi-tools' for using on a range of foods - like the chisel-like teeth of rodents, or the toothless beaks of birds. Even as fishes with comb-like teeth are restricted so as to not consume certain items, they can have either broad or narrow feeding habits, and eat either animal or vegetable resources.

Centropyge have teeth adapted for benthic grazing, and they resemble blennies and mbuna in this respect. They are among the most herbivorous angelfishes, but their diet still includes sponges and tunicates, and again dietary isotopes indicate extensive omnivory exists in these fishes. In the aquarium they do nip at coral polyps and clam mantles, so they ought not to be regarded as 'reef safe'. The Paracenteopyge angelfishes are basically carnivorous by nature. They should not be confused, ecologically speaking, with the dwarf angelfishes of Centropyge proper, or the pygmy angels of the genus Xiphypops; but their diet is not well documented in the literature, only that they eat sessile animals, and although the can be encountered in the shallows, they are more often associated with deeper reef habitats.

Xiphypops, the pygmy angelfishes, are different from the Centropyge angels, because natural selection has helpfully reorganized the orientation of their faces for a lifestyle of herbivory by dislodgement. Although I have again heard of pygmy angels nipping at tridacnid clam mantles, they are by far the safest of the angelfishes in coral aquariums. They simply possess too much specialization for a specific type of herbivory, for them to destroy corals. Again I offer the caveat that these animals may sometimes nip at fleshy polyps, although I have never witnessed this. Truthfully, the pygmy angels are specialised, obligate consumers of delicate and foliose algae, which they eat using combing and shearing strokes of their downwardly inflected jaws.

Two other genera of angelfishes can be considered, on phylogenetic grounds, to be allies of the dwarf angelfishes; these are Apolemichthys and the surprisingly planktivorous Genicanthus, or swallowtail angelfishes. Members of the delightful genus Apolemichthys are understood to be omnivores, with a diet that is dominated by sessile animals; specifically, some 3/4 of their diet in the wild is spongal. The diet of this genus in the wild, is not so well studied as some of the other angelfishes, although these are wonderful fish indeed. Whereas their allies Genicanthus have abandoned their lifestyle of benthic feeding, and they display evolutionary reversals associated with open water planktivory. Genicanthus are thus the most extreme outliers of the angelfish group, in terms of their unique feeding ecology and behaviors. For this basic reason, these specialists are considered to be entirely 'reef safe' among the angelfishes. All the same, Genicanthus in the wild are known to consume some benthic algae and sessile animals. To my knowledge they never eat anything that we would think of as corals when they are in the wild, and I regard these specialists as about as appropriate for reef aquariums, as are Xiphypops.

At the other end of the spectrum of specializations that are observed in pomacanthids, is the regal angelfish, Pygoplites. For Pygoplites are the most specialised of all angelfishes for a life of gripping and tugging tunicate and spongal masses, to the point that wild Pygoplites will consume nothing else at all. Nonetheless, aquarists have sometimes noticed that they appear to bite at 'softies', a non-zoological catch all category, that contains all popular anthozoans that neither secrete a stony skeleton, nor large actinarian anemones. Obviously the behavior arises out of frustrated instincts when it occurs, and at least in some cases, the angelfish is likely biting encrusting organisms near the base owhere the 'softies' are attached. Observations that fish happen to bite at coral are not necessarily observations that they eat corals; they can be eating items on their surface or near their base, and people should bear in mind conclusions based only on superficial observations, ought not to be jumped to.

The butterflyfish-like Chaetodonplus are quite reef safe angelfishes, although they have been reported to bite at the fleshy polyps of 'LPS' type colonies, and also at clam mantles. This is even though their basic diet in the wild is spongal and algal - and stable isotopes have determined that they also consume detritus deliberately, making them scavengers. Nonetheless Chaetodonplus are safe in aquariums that feature stony corals with short polyps. Different individuals appear to vary in their destructiveness to other corals, and I had no trouble with mine in a mixed reef. But other people have reported they inflict regular nippings upon fleshy, sessile ornamentals. Aquarists tend to classify their stony corals into the two non-phylogenetic categories, SPS and LPS, but they are poor predictors of coral vulnerability, because the categories ignore the stings and other defences of polyps. However, because angelfishes have evolved to grab and tear at bulky items, large polyps will be at potential risk of angelfish attack, whilst those coral colonies bearing small polyps will not.

The 'large angelfishes' are two wonderful genera of fishes that have long enthralled aquarists - Holacanthus and the archetypal Pomacanthus itself. Before the rise of reefkeeping, the large, showy angelfishes were staples of saltwater fish retailing. When the hobby refocused on smaller systems, small fish, and living corals, they dropped from popularity. And some of the large angelfishes, as omnivores, actually do eat anthozoans by their nature. The subgenus Euxiphypops - unlike their smaller namesakes - are typical angelfishes, as regards their jaw mechanics. However they too have evolved into a herbivorous ecological space, and their faces are able do deal with tough seaweed as a basic diet; they use the same eating techniques that other Pomacanthus angelfishes more normally employ to exploit ruggedly attached, sessile marine animals.

All large angelfishes are disinterested in corals that have branching forms, which means that well established gorgonians and 'SPS' with this growth habit shall be entirely safe from those impressive grazers. However large angelfishes are well known by aquarists and marine biologists, to consume both 'softies' and sometimes fleshy 'LPS'. Polyps the size of zoanthids may be swallowed whole by big angelfishes, and even large anemones may be eaten - and even if they are located in an otherwise inaccessible, well protected position. Large angelfishes are fortunately suited to 'SPS' tanks, although they have evolved to consume anthozoans as omnivores - thus, it is their nature.

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I cannot believe I have not written before, about the wonderful carps of the genus Garra. These bottom swimmers are the genus that includes the famous, so-called 'doctor fish' (or 'nibble fish') of Turkey. Sadly these fish fo not eat vertebrate skin, and cannot live on such a diet; they starve unethically for human selfishness, although one imagines the traders are not aware of the unnecessary suffering, as they need to replace their fishes often. The fad for 'doctor fish' seemingly began with localized ethno-zoological knowledge in Turkey, as regards populations of the red garra, Garra rufa, which is widely regarded nowadays as a species complex: it is not clear exactly which of the fish in our aquariums, belong to which recognized or proposed species. The aquarium G. rufa have been considered to be a domesticated strain.

This is typically a 14 centimeter or under 6 inch long carp, but the species is actually variable, and some populations produce individuals as long as 24 centimeters, or neatly 10 inches. Reportedly the common aquarium strain from Hamam Creek, near Sivas in Turkey, grows to only 10 centimeters or 4 inches long. The broader G. rufa has a distribution through the Levant and eastwards into regions of Iran. Typically they inhabit moderately to fast glowing West Asian rivers, with rocky and gravelly bottoms. The range of this species is quite broad, and local races or subspecies may be recognized across this range.

Garra sp. are grazers by habit, and they are equipped with a downturned mouth for this purpose: in fact the lower jaw possessed a sectorial pad, that they use to brace themselves against currents, by clinging to hard substrates. As with many other bottom dwelling or benthic fishes, their swim bladder - the floatation device of typical fishes - has become reduced. Without doubt, Garra sp first evolved in upland streams, and other flowing waters, but they are able to colonise and survive in slower flowing to still water environments. G. rufa tends to avoid stagnant waters,although it is more tolerant of turbidity in the wild, than are some other species of Garra

Like many other benthic carps, Garra sp. are peaceful fishes that have evolved graze on biofilms. The items that they regularly ingest include diatoms and cyanobacteria; the amount of animal protein on their natural diets is low, and is incidentally ingested. Garra sp. are not problematic to feed, as long as their dietary intake is basically vegetable based, and it is obvious that cannot subsist only on human skin cells; such behavior is an expresion of their grazing instinct when they see an object that can be grazed on.

Naturally these grazers eat food from the bottom, so sinking items would be most appreciated by these fish; they ought to contain spirulina or similar. But ideally the aquarium should be allowed to sustain enough algal biofilm for these vegetarian carp to graze upon. Reportedly they will consume the same fresh and blanched fruits and vegetables that are commonly offered to herbivorous, grazing fishes. For example, spinach that is first blanched is a long established staple diet for algivorous fishes; but really, the aquarium should already be able to feed algae grazers before they are introduced.

As regards temperatures, the G. rufa of Kangal stock are beng kept healthy by aquarists within the temperature range of 15 to 28 degrees centigrade, and 20 to 23 degrees would probably be suggested by field data from their ordinary habitats. Apparently, the fish in the Kangal springs are active and feeding as 35 and 36 degrees, although for their safety, the water temperature should not be allowed to exceed 38 degrees - which is an impressive upper limit for a geographically non-tropical fish, and is stunning for one that may be kept all year round in a comfortable room, without supplemental heating.

In the aquarium, their water ought to be of good quality, although wild G. rufa can tolerate more turbidity than do some other Garra species. and the average pH of the Kangal springs is 7.2 to 8. Despite the rheophilic origins of Garra sp. the water does not need to be strongly flowing, as long as it has reasonably good water quality. As community fishes, G.. rufa are peaceful to other species, and to one another, other than that they may reportedly become boisterous, when their food is limited; they should be accommodated together in numbers to reflect their gregarious nature. Their habit is to hide among stones and vegetation, when they are not feeding and moving, do the aquascaping ought to provide them with retreats.

Since the 'doctor fish' fad led to an ethically questionable boom in 'fish pedicures' or ichthyotherapy, the genus Garra has become more popular as useful and characterful bottom living fishes for home aquariums. A number of delightful species are now sold in aquarium stores, most of them originating from lands further east than the range of G. rufa itself. But it is the world famous Kangal population of G. rufa that have awakened popular interest in the Garra clade, and they do appear in the aquarium trade

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The curious fish that is called the hogchoker, Trinectes maculatus, is one of the few true flatfishes or pleuronectiforms, that are encountered in the aquarium trade with any regularity. In North America, where the species is native - for it is distributed from Massachusetts down to Panama - wild caught hogchokers turn up in retailers tanks fairly regularly, where they are usually sold as 'freshwater flounders'. Elsewhere else, this species is quite an infrequent import, and those flatfish that are explicitly traded as freshwater soles or flounders, at least in Europe, are more likely to belong to truly freshwater species indigenous to tropical South America, Asia and Australasia.

None of them is imported with great regularity, but in North America, it is wild caught juvenile hogchokers that are the flatfishes most often traded as a freshwater fish. This is not entirely accurate, because although the mature hogchokers can be found far upstream, juveniles are more strictly brackish fishes in the wild, inhabiting only estuarine waters during the summer months. Hogchokers are almost always sold when they are small individuals, for which a brackish setup would be more authentic. Juvenile hogchokers actually do survive and grow in freshwater environments, but such is suboptimal for their growth rate, and this is because freshwater creates higher metabolic stresses for them. Ideally, little hogchokers should be maintained in mildly brackish aquaria, and at a temperture of perhaps 22-26 degrees centigrade, based on the summer water temperatures that wild hogchokers this size would regularly encounter in their natural habitats.

Adult hogchokers show no preferences of salinity at such temperatures, being fine at a specific gravity of 0, or freshwater, upward to 1.02. in parts of their range, wild hogchokers experience water temperatures that may be quite low during the wintertime, but rising as high as standard tropical aquariums in the summertime. When they are kept at a temperture of 15 degrees, hogchokers grow best at a specific gravity of 1.01 to 1.02. Curiously, at the warmer temperatures that wild hogchokers might encounter in the southern part of their distribution, they puts on more weight when they are living in freshwater conditions.

On average, the hogchoker grows only to about 10 centimeters or 4 inches long, although individual fishes of twice this length are recorded, reaching a length of 20 centimeters, or 8 inches. These are small flatfishes, and they take only small prey in the wild, where they consume annelids, arthropods, and molluscs. Trinectes may need acclimatising to a frozen captive diet, but this can certainly be done, and they consume suitably sized meaty morsels. It is unlikely they will adjust to eating dried rather than defrosted foodstuffs, although it is not exactly unknown

The hogchoker is common on soft, sandy bottoms where it burrows itself in classic flatfish style, and it is also rokerant of still finer grained mud or silt bottoms. Such a fine substrate should be replicated in the aquarium, because hogchokers use the substrate to conceal themselves and this makes feel safe and relaxed. Flatfishes may be bothered or even injured by fishes that bite at the substrate, or are highly active at the bottom of the water column. Naturally, as predators, hogchokers in the aquarium may themselves consume small tankmates, so cohabitants must be too large for the flounders to see as prey.

By and large, however, hogchokers are not in the least confrontational by nature, and they may be considered reasonably indifferent to the activities of other fishes, using the water overhead in the same aquarium Although hogchokers camouflage themselves well, and are not very active, this very crypsis and their fascinating, asymmetrical anatomy make them a great, quiet oddball species, for those who accept these fish have specific care needs in our home tanks

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Today I was aware someone had imported a cobitid they were trading as a moosefaced loach. The species in question is more traditionally called the gongota loach, Canthophrys or Somileptes gongota, from shallow and slow-moving streams in northern India, Nepal, and Bangladesh. Reports of its natural presence in the state of Orissa, in eastern India, seem to be false. This species is best documented from piedmontane hill streams. They can also be called a moosehead, or even a jaguar loach.

This species grows to about 13 centimeters, or 5 inches, and is thus a nice size for many home tanks. It is considered quite an uncommon loach in its range, and the extent of its natural distribution is disputed among ichthyologists. Gongota loaches have a reputation among aquarists, as a very difficult species to maintain alive. However a minority of loach keepers have reported that this species, when it's needs are provided for correctly, can be undemanding.

According to the literature, mooseface or gongota loaches are reportedly present indiscriminately on muddy, sandy, and gravelly bottoms in the wild, although they are of benthic habits as would be expected of a loach species. However these loaches definitely feed by sifting through fine substrates, and thus they require a sand substrate in order for them to behave safely and normally. When they are in our aquariums, they definitely fare far better when they have access to fine silver sand substrates, which facilitate certain of their natural behaviors.

These include their habit of self-concealment by burrowing activities, and for this reason their eyes are positioned quite dorsally and elevated. Such a configuration of the face allows them to spy above the level of the sand, whilst they are otherwise buried safely out of the view of predators. Decor is therefore not essential to them as hiding places, as long as they can burrow into the sand to hide, which is exactly as they would do when in the wild. These are a very demersal fish indeed.

Some aquarium literature claims that this species requires cooler water, for example a temperature of 18 to 22 or 16 to 24 degrees centigrade Such matches recommendations and norms for sympatric species, as the small carps Danio rerio and Pethia ticto. However its natural range extends a bit further south than some people seem to assume, and it appears not to be strictly a piedmontane fish, as some people maintain.

With this species, perhaps, their location of origin should be used to determine the proper temperature for these fishes, if this may be possible. In fact in southern parts of their range, the temperature of the water averages at 25 to 26 degrees centigrade, and seasonally may drop closer to 20, ànd rise nearer to 30 degrees. In these waters, which are always flowing but not too powerfully, the pH is between 7 and 8, and thus circumneutral whilst leaning towards the alkaline side. This is contrary to some online opinion, that this species requires very soft and acidic water.

The feeding habits of gongota loaches are to sift morsels such as insect larvae from a fine substrate, expelling the non-food ingesta via their gills and retaining edible particles for digestion. Therefore the most appropriate diet for these fish, would be small, defrosted foods of suitable nature, or sinking dry foods if they will accept them. Although newly imported gongata loaches have a reputation for being difficult to feed, and generally for dying after importation, they can fortunately adapt to eating dry preparations.

With their own species, gongota loaches gregarious, and they are properly housed together in groups. Although they are very tolerant and peaceful by nature, their feeding habits can complicate their care in the ordinary community tank. This is because many other fishes are eager to snatch the same first of food items, that the gongota loach needs to eat, and their nature is to feed only at the bottom of the aquarium. More active fishes that are present in the same aquarium as gongota loaches, might eat the available food before the nocturnal sifters can access it.

Otherwise feeding these loaches is unproblematic, assuming that they have already been acclimatized - provided that the food particles they are offered are sufficiently small in size. They can even take to eating flakes once they have become waterlogged and sunk to the substrate. Gongota loaches seem to be a fish that perishes too often through the importation process, but are not in principle difficult, as long as certain special needs they have, are anticipated and provided for.

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Some other coldwater freshwater fishes appear irregularly in the pond and aquarium trade, beyond domesticated goldfish and koi varieties. Whilst many of these lack color, they may have bags of character, and interesting behaviors. One such fish is the miller's thumb or European sculpin, Cottus gobio. This fish normally grows only to 10 centimeters or 4 inches, and sometimes quite larger, to 18 centimeters,or a little over 7 inches. Even this is not huge, so they do not require raised indoor ponds or other massive aquariums. From the perspective of European aquarists, this is a true native fish, having a natural distribution over a swathe of Europe, including its presence on Great Britain.

Their habitat preference is for well oxygenated streams and rivers, with coarse beds featuring large stones. Although these sculpins are found in rapids, they have a preference for moderate flow. It is their behavioral selection for useful slack water refuges, and obstacles to uncomfortably high flow velocity, that enables their presence in faster flowing, upland headwaters. Younger fish prefer shallow, stony riffles, whereas the adults have broader habitat preferences, and can be found present in the wild around submerged wood and vegetation, in lakes and in slower flowing waters with softer bottoms.

Sculpins are a part of an important radiation of fishes known as cottoids, that also includes the lumpsuckers and greenlings, among some others. Traditionally the cottoids were regarded as a subclade of the scorpaeniform fishes, but the characteristics supporting that 'order' or 'suborder', were few and problematic, for example, their spiny cheeks. Cottoid fishes have turned out to be more closely related to the sticklebacks and eelpouts, than they are to the core scorpaeniforms, or the true scorpionfishes and their allies, which sculpins can certainly resemble.

Cottoids or sculpins are benthic fishes of marine to freshwaters, that lack a swim bladder, which is not unusual for fishes that live on the bottom, because it is a floatation device. C. gobio tolerates broader water requirements, than is often said to be the case. The pH of the waters they inhabit in the uplands is around neutral, but they can migrate down to lowland chalk streams, where the pH is 9, so these are fish of hard and base freshwaters. Although this species can be found in the low salinities of the eastern Baltic Sea, no elevation of specific gravity is necessary in the aquarium, and they are basically freshwater sculpins with a limited tolerance for low end brackish conditions.

Much is said online about the supposed demands of these sculpins for very cool water, and I have read the curious assertion that thejuveniles are more heat tolerant than the adults. Contrarywise, juvenile C. gobio are in fact less tolerant of higher temperatures, than are the adults of their species that have migrated away from riffles, and they become thermally stressed even below 20 degrees. The range of water temperatures at which mature C. gobio feed is as low as 5 degrees and also as high as 26 degrees centigrade.

C. gobio basically have a staple diet of arthropods. Older sources overstate the extent of their predation on fish eggs and fry, though with that said, they actually do consume such items opportunistically. Sculpins such as C. gobio are able to ingest large food items, and smaller ornamental fishes may end up as prey. C. gobio are territorial and aggressive among themselves, and prone to conflict with other bottom living fishes. Conflicts can be minimized by providing these fishes with a complex aquascape, in which lines of sight are easily broken. Stones, gravel, wood, and live water plants, are all appropriate for this species Sculpins are normally ignorant of dissimilar fishes with different patterns of spatial use.

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Though it may not be the showiest of the butterflyfishes, the threadfin butterflyfish, Chaetodon auriga, is strikingly pretty and popular in its own right. Reportedly threadfins grow to a size up to 23 to 25 centimeters, or 9 to 10 inches. In reality, although specimens this size do exist, it is rare to find any that are this size, in either aquaria or wild environments, although they regularly reach a size comparable to an adult human hand. C. auriga has a vast range from the Red Sea and the eastern shores of Africa, across into the Central Pacific Ocean, including isolated archipelagos such as Hawaii. Across this range the species is of variable appearance, but these morphs seemingly cannot be correlated straightforwardly, to either geography or phylogeny. Although the absence of the spot upon the dorsal fin, among the nominate C. auriga populations that live in the Red Sea, does seem to be a localised, racial trait.

The great clade of chaetodontids or butterflyfishes is very diverse on the reef, and they are thought of as the primary clade of coral eating fishes. However not all of these animals consume corals obligately, or at all, and basal genera like Heniochus have faces that look and function rather normally for reef fishes. The Chaetodon subclade have derived facial anatomies favoring increased coral feeding, whilst certain other butterflyfishes such as Forcipiger and Chelmon have evolved in a very different direction, towards probing behaviors in foraging, so like some insectivorous mammals and worm eating birds, their snouts became elongated. C. auriga is a member of the Chaetodon clade, but it too shows evidence of natural selection towards a long faced, probing morphology. Not surprisingly C. auriga is sometimes described as what is called a 'faculative corallivore' or an adaptable animal that can either eat corals or do without them as a food source. Confusion surrounds it's corallivorous abilities, and it is sometimes alternatively classed as a 'non-corallivore'.

Threadfin butterflyfishes are restricted, when they are juveniles, to the sheltered environments of lagunal and near-shore patch reefs, before moving slightly further afield when larger. Juveniles of the species show little particular association with any live coral, and the species can be considered to be a habitat generalist. The adult fishes have even broader tolerances. C. auriga is found in weedy and other areas of low coral cover, as well as with lush coral growths, being considered associated with areas of natural coral rubble. Whereas in the aquarium C. auriga have proven easy to feed and resistant to diseases. They are reported to - only sometimes - consume Aiptasia sp. anemones, and definitely consume other species regarded as harmful to corals, such as certain nudibranches up to 3 centimeters.

C. auriga forages for benthic items on hard substrates, and its diet includes marine arthropods, annelids, and even macroalgae. Earlier works present C. auriga as even more omnivorous, explicitly labelling the species as a 'benthic omnivore' subsisting also on octocorals, actinarians, and scleractinians. Stable isotope study has suggested the very low importance of corals or anemones in the wild diet of C. auriga, but observations of such should not flippantly be dismissed. Small polyps are definitely grazed from the shells of live clams by this species. Observations of bites at corals might not necessarily demonstrate the deliberate ingestion of coral tissues, and gut content analyses can fail to identify the ingestion of anthozoan tissues. In any case C. auriga mostly bites at substrates other than growing coral colonies.

C. auriga forages prey mostly around coral rubble, and in and around holes and ledges, as is predictable by looking at its face. Its method of feeding has been categorized as a 'grabber-tearer'. Although the labial teeth of C. auriga are spatulate, they are not especially robust as they are in the true coral feeding grazers. With that said, the butterflyfish tooth morphology remains surprisingly stable given their various dietary specializations. But similarities of specialization within the group have been noticed, between the craniodental morphology of C. auriga, and those of the probing butterflyfish genera, Forcipiger and Coradion. Coral feeding in butterflyfishes leads in a different direction, towards the evolution of increasingly short faces with stronger jaws, which are more suited to the tearing of polyp flesh.

The reputation of C. auriga as feeding on corals makes it a questionable species for the reef aquarium. But it is not open for debate that C. auriga also controls organisms more harmful to coral, in the manner of certain wrasse species. More often than reports of this species feeding on corals in the aquarium, they are alleged to bite tridacnid clam mantles, and the crowns of large tubeworms. Similar behaviors are noted in other species of butterflyfishes that are classified as members of the same feeding guild. Conversely they are proven to harmlessly browse epibionts from the shells of pteriid clams, and similarly from the surfaces of holothurians - behaviors that are easily misobserved.

Interestingly it is observed that in the wild, C. auriga do not attack diseased colonies of Acropora corals, although these became a feeding magnet even for ordinarily non-coalrallivorous fishes, such as damselfishes, wrasse, and gobies. So it might seem that C. auriga is a species harmless to Acropora colonies, which belong to the genus perhaps most celebrated in reef aquariums. Perhaps they create some incidental damage by biting them, but only to take prey from their surfaces. Also no butterflyfish species appears to attack the stinging Euphyllia corals, which possess a potent venom and are thus highly protected against most coral feeding fishes.

As foragers of benthic food sources, butterflyfishes are broadly ecologically comparable to fish such as grazing acanthurids. Fishes belonging to such benthopelagic guilds require decent swimming space in the aquarium, but also an aquascape sufficiently complicated that they might comfortably dart into its nooks, should they feel alarmed or intimidated. In the wild this butterflyfish readily takes refuge among live corals. Feeding of C. auriga in the aquarium is easy with the meaty, defrosted items that are available. In my experience they will even accept such preparations as floating flakes. Towards other fishes they are passive, although they can be victimized by boisterous or nippy species, so tankmates must not have such demeanors.

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The popular and stunning fire eel, Mastacembelus erythrotaenia, is a very large spiny eel from Southeast Asia, that is on record as growing to 100 centimeters, or 40 inches. In the aquarium and also in the wild, their growing 'only' to a length close to 65 centimeters should be expected, however the species is still on record as the largest known spiny eel, although the M. armatus complex is suggested to sometimes reach similar lengths of about 'three foot'.

M. erythrotaenia is a fish associated with riverine environments, although it avoids fast flowing water, and it is also encountered in inundated, lowland floodplains. In these freshwater habitats, it shares the typical spiny eel habit of burying into mud, by horizontal movements of their sinuous physiques. When they are buried, spiny eels often allow their snout and tail tips to protrude upwards.

Other than its great size, M. erythrotaenia is, in fact, quite a typical spiny eel, and within that clade, it is difficult to misidentify as any other species. This is fortunate because confusion generally surrounds the identities and nomenclature of Asian spiny eels. M. erythrotaenia is a widespread, tropical species, found in a wide swathe from Indochina, down through peninsular Malaya, and into western Indonesia. The fire eel is apparently absent from northern Indochina, including the more northern regions in Thailand and Vietnam.

I grew up with aquarium books telling us that spiny eels are aggressive, difficult to feed, and too large for home aquaria. Thankfully this is all exaggeration, and partially based on confusing the clade with some other teleosts that are called 'eels'. Which, incidentally, do not form a natural group of fishes, so that only members of the unrelated anguilliform clade are truly eels, and the spiny eels are much more closely related to the gouramis and snakeheads. The similarities of form and function, that are seen in both anguilliform and spiny eels, result from convergent evolution.

Spiny eels or mastacembelids, are their own clade of fishes, closely related to the synbranchids or swamp eels, with which they share their eel-like morphology and digging habits. Though they will consume very small fishes, and especially fry, Mastacembelus sp. are essentially predators of other benthic organisms, such as aquatic insects and annelids. This species does not seem to consume vegetable material habitually.

These are sought using olfaction, for which purpose the spiny eels possess tubulated nostrils, a visually remarkable synapomorphy, that marks them apart from other fishes of an otherwise similar, eel-type form. Although they are sometimes described as bearing a proboscis, the facial appendage of spiny eels does not qualify, because it is not an organ used to hold and manipulate food, as are the true probosces or trunks of tapirs and elephants.

However, it is a flexible tentacle, supported by an elastic cartilage which even has a synovial articulation with the bony facial skeleton, where the associated musculature attaches. In this sense it really is comparable to mobile mammalian snouts. Spiny eels are adept foragers, equipped with a good sense of smell and a usefully sensitive tentacle tip, that they use to explore their surroundings.

Other traits of spiny eels include their dorsal spines, which are in fact specialized fin rays. When they feel themselves threatened by a larger predator, spiny eels position their bodies so that their spines form a sharp, defensive saw edge. Fearful spiny eels can wound the hand of a careless human handler, damage the aquarium nets used to catch them, and sometimes even puncture the plastic bags used to transport them. Therefore any nets employed should be deep and soft, and double bagging should be used when transporting these prickly fish.

Spiny eels are primitively capable of breathing atmospheric air, which explains why some species are present in difficult environments. They differ in their craniofacial appearances, but only as variants of the basic, stable spiny eel theme, such as the extents of the rostral organ and of the jaw musculature, which relate to finding and dealing with food.

Naturally the substrate provided for spiny eel species, should be soft, to facilitate their natural digging behaviors, although at achieving larger sizes, this species seems to burrow less. Large decor should be provided to create shelter for these fish, especially during the daylight hours. Heavy items must be placed in the aquarium before the addition of substrate, lest the digging of the tank inhabitants lead to an accident. Sharp substrates must be avoided

Leaves and wood are appropriate decor, per the wild biotopes that are known to be frequented by M. erythrotaenia. Although they are not herbivorous, their digging behaviour is likely to uproot any plants that are rooted into the substrate. Floaters and underwater epiphytes should however be fine, but mighty spiny eels are not ideal denizens, for most kinds of richly planted aquascapes.

The lighting should be low, or diffused by floating plants,and any lid tightly fitting, lest the 'eels' escape. The often repeated statement that this species prefers a pH value between 6 to 8, is consistent with the presence of the species, in localities such as the Chao Phraya and the Mekong. Some records confirm it's ability to tolerate waters with a pH as low as 4.6, and a temperature as high as 30 degrees centigrade

Some sources suggest that the pH becomes suboptimal for this species, when it is elevated above 7.5, abd that the water temperature should be 27 to 29 degrees centigrade. But I am aware that at some wild localities where M. erythrotaenia is present, and seems to be flourishing, the pH is as high as 7.7 or 7.8, anf the temperature there is 25 to 27 degrees centigrade.

Because M. erythrotaenia can be territorial among themselves, it is often stated that they should not be kept together, but from experience, more than one adult of this species may safely cohabit, and they will even share a hiding place together. Like other spiny eels, this species is fine with unaggressive fish that will not fit into its mouth. They mix well with big, schooling cyprinoid species from their area of origin, including tinfoil barbs and clown loaches

Feeding M. erythrotaenia is actually straightforward, using defrosted foods of meaty composition. When chopped to am appropriate size, seafood from the fishmongers can also be used to provide for these slow benthic carnivores. Also fire eels will happily take to accepting sinking pellet preparations, if they apt for insect eaters. Other than the constraint caused by the dimensions of their mouths, fire eels are generalist carnivores and they are not fussy once they feel settled in.

However when they are freshly imported, spiny eels have a reputation as difficult fishes to feed, and newly arrived imports are more likely to be shy, and to eat only when the lights go out. Until they are feeding more boldly, active benthic fishes like loaches and catfishes, might well take all their food first. With slow and reluctant feeders, the choice of tankmates thus matters

Newly imported spiny eels are also vulnerable to stress and injury, from the process of collection and shipping. Fortunately they all acclimatize to aquarium diets with time, contrary to old misinformation that they will only eat living prey in the aquarium. Their actual care is not hard, assuming that healthy and bold individuals are chosen, particularly long term captives, and their needs are adequately and easily provided.

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Other than perhaps the common clownfish, and perhaps the common cleaner wrasse, no fish of the reef is so iconic worldwide, as is Zanclus cornutus, the Moorish idol. Usually measuring just over 20 centimeters, or 8 inches long, with a deep and narrow body that is 1 to 1.4 times its standard length, this otherwise disc shaped fish has an elongated, protrusive, tube-like snout; a very long, trailing, banner-like extension of its sickle-shaped dorsal fin; and a pair of facial projections that are more pronounced in the males of Z. cornutus. The Moorish idol has two broad black bars on its body, and a yellow saddle across its snout.

This species is omnivorous, but grazes on animal material, especially sponges, moreso than it feeds on algae. However its gut resembles that of herbivorous surgeonfishes or tangs of the clade Acanthuridae, such as Zebrasoma. Although Z. cornutus is normally regarded as the sole member of the entire family Zanclidae, there is also a history of placing it in this same, larger family of fishes. The issue is little more than semantics, because everyone agrees that Zanclus is very closely related to acanthurids, with its bones, teeth, and soft tissues all demonstrating a special evolutionary kinship, that is also confirmed by molecular studies. Zanclus is essentially a descendant of primitive tangs, that diverged ecologically from the true acanthurids, when it began adding spongal growth to its ancestrally more herbivorous grazing habits. Zanclus even today grazes on algae as well as sessile animals.

Moorish idols inhabit lagoons, reef flats, and clear, seaward reefs, throughout its widespread Indo-Pacific distribution, in tropical and some more temperate waters. They are found in the wild from the eastern coast of Africa, through to the eastern Pacific, and from Japan to Lord Howe Island and the shores of mainland Australia. The substrates they associate with may be either soft or hard, and the water can be either turbid or clear. They associate with both rocky and coral reefs, both coastal and offshore, and they are present around man. Despite their reputation as fragile in the aquarium, Z. cornutus are both versatile and adaptable in the wild, and the species is predicted to become a beneficiary of ocean warming by human activities. They are sufficiently adaptable to be present in human modified coastal environments.

The Moorish Idol has a reputation as impossible to keep alive in captivity, and it is rightly considered ethically wrong to import fish that are not likely to survive in captivity. The reason the species rarely lives long after its live importation, is in fact due to the trauma it suffers during the lengthy process of capture, holding, and long haul shipping. The chief stress on these fishes being starvation, during the whole process`by which they arrive to our tanks. If Moorish idols are not so stressed, or if they long ago survived this whole process, these fish are not actually problematic to look after, so there is no need to fear for their welfare should one be found that needs rehoming. It is said that this species either thrives and eats anything and everything in the aquarium, or they tragically die shortly after arriving, despite their cost. Fishes that are long term captives, however, are expected to be hale and healthy, and feeding vigorously.

The Moorish idol is often seen in pairs or groups of three fishes, although it is sometimes seen alone, and the species may form larger aggregations described as large schools. A small number of Z. cornutus can cohabit in the same tank, provided that it is large enough for this. In the aquarium, Z. cornutus is usually benign towards other fishes, but can be bold if challenged by another species. Known fin nippers and habitual bullies are not suitable as tankmates for Moorish idols. There is definitely a possibility that, as grazers, a Moorish idol could damage ornamental benthic organisms, such as coral polyps. According to anecdotes, very noxious and strongly stinging species of coral are left alone, such as the genera Palythoa and Euphyllia. Although they reportedly do sometimes consume even hard corals with small polyps, it is easier for them to target the polyps of fleshier species, and it is sponges, tunicates, and macroalgae are its dietary staples rather than polyps. Because the natural diet of these roving grazers features both animal and algal components, both kinds of food sources should be included in a varied aquarium diet for this fish, which ought to be fed little and often through the day. Newly imported Moorish idols, sadly, are not expected to take to feeding readily.