A visual guide to butterflyfishes

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They’re fish that don’t fit into many modern marine tanks, but they still appear in retailers across the country. Meet the attractive but tragic butterflies.

Graceful, flitting and delicate — the name butterfly is more than apt for these fishes. With around 130 species spanning 12 genera, you’d think there’d be a butterflyfish for any marine tank.

Alas, a combination of niche dietary requirements and an inexplicably high susceptibility to disease means that the majority of species are beyond the scope of even the most advanced aquarists. Yet they prevail. They prevail in stores across the country, and they prevail in home aquaria with mixed fortunes. Through decades of aquaristic trial and error, we have whittled down to a shortlist of ‘possible’ marine tank residents from the family. Of those, some are known to be generalist feeders with tough (by butterfly standards) hides. Some are still shaky ground, hit-and-miss jobs where you’re. as likely to acquire a willing feeder as you are a fish that starves itself to death. We can, at the least, make relatively measured guesses at those that might work in some circumstances.

Suffice to say, when purchasing any butterflyfish, make sure you are fully aware of how it feeds — the more obscure diets can run to specific species of coral polyp, or even sponges, without which the fish has no chance of survival. Their long snouts serve a purpose, usually to reach deep into crevices or to pluck polyps from within the tangled branches of nested corals. The mouths are fragile and prone to damage through rough handling, possibly one of the more common but lesser-appreciated reasons for their high mortality rates in aquaria.

The corallivore nature of so many butterflyfishes immediately raises the question of where they fit in the modern hobby. Sure, in the dark ages of fishkeeping, when tanks were all crushed cockleshell substrates and decorative Acropora coral skeletons, they fit in fine (until they starved). But the fish-only system is a dying breed, with most marine aquarists now focusing more on their corals than their fish. Be wary of anyone who tells you of ‘reef safe’ butterflyfish; this is something of an oxymoron, and even a single individual can do considerable damage to a home colony.

A couple of exceptions, perhaps, might be those long-beaked fished of the Forcipiger and Chelmon genera. Sometimes peddled for their utility in plucking Aiptasia from soft coral set-ups while ignoring the corals themselves, the word on the street is that they tend to be less straightforward, either eating neither or both. Obviously, impeccable water quality is required in the home setting, but even with the best conditions in the world, select your purchases carefully. Look over every millimetre of a fish prior to buying it and reject any with even a single spot of Cryptocaryon (marine whitespot). Finally, avoid buying fish that are either obviously small juveniles or full-grown adults (Under a third or over two-thirds their eventual adult size). Anecdotally at least, this seems to be crucial to transporting and settling them successfully.

Read the rest of the feature in the March 2022 issue. Buy the latest digital edition and read instantly on your computer, mobile or tablet device.


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