Closely-related to the Pufferfishes and Filefishes, the Ostraciidaea family of Boxfishes sits within the Tetraodontiforme order. Fish in the family are known variously as Boxfishes, Cowfishes and Trunkfishes and there are about 23 species across 6 genera.

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These fishes are particularly interesting not just for their outlandish appearance but also for their ability to secrete cationic surfactants through their skin which can act as a chemical defense mechanism. This is particularly important to note if planning to keep a boxfish with other fishes as this toxic mucus may be released if the fish is severely stressed and can dissolve quickly, killing other organisms rapidly in even a large aquarium. They are also interesting for the hexagonal plate-like scales that are fused together into a solid, triangular or box-like carapace, from which the fins, tail, eyes and mouth protrude. In general, young specimens are brighter and more rounded in appearance indeed some species can look cute when small but grow to very large sizes, and change appearance considerably.

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Ostracion genus – with 10 species, this is the largest genus in the family. It also contains the species probably most familiar and available to aquarists; O.cubicus. What many aquarists don’t realise is that the cute baby or juvenile boxfish usually offered for sale may grow very large and require special conditions. The adults often look very different to juveniles and this applies to different sex fish also. To avoid stressing these fish (and the release of poison in worst cases) they are best kept in quiet tanks with low to moderate water movement, excellent water parameters, no boisterous or fast moving tankmates and plenty of caves and crevices. When feeding, a sinking food should be used to avoid the ingestion of air at the water surface. A variety of foods will be taken. Due to the often extreme difference between different sex/age individuals, the gallery below has individual thumbnails for different forms of the same species, to aid identification.

Lactoria genus – of the 3 species in this genus, only L. cornuta is frequently available, usually at a small size. It’s worth knowing that, although cute and interesting, they can attain up to 50cm! This genus is similar to other boxfishes in terms of captive care.

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