Hippopus porcellanus

No source consulted describes keeping this species in an aquarium: the advice below is what is published for traded giant clams and still needs confirming for it. Acclimation: invertebrates cope badly with even small changes in water chemistry, and clams are sensitive to salinity changes. Acclimate it slowly, by floating and then drip, and never rush the process. It must then get used to the light: a clam under 5 cm has a thinner mantle and is more sensitive to very intense lighting. Start it on the bottom, on a small rock or in a dish of coarse substrate, then move it up gradually, as you would a newly added coral.

Setup: as an adult it lives free on the bottom, without a byssus, in shallow water; a sand bottom would therefore suit it, as it does H. hippopus. No source consulted mentions farming or an aquarium trade for this species.

Tankmates: it is a peaceful animal that harms nothing, but in an aquarium anemones, triggerfish and puffers may attack it, and a wandering anemone may sting it. Inspect it before adding it, and quarantine it if you can, to spot parasitic Pyramidellidae snails: they are white, conical, a few millimetres long, and feed on the clam on its shell and foot until it weakens or dies. Remove them by hand (a toothpick will do), checking day after day; the wrasses Halichoeres melanurus and Halichoeres chrysus eat them.

Health signs and sensitivities: the mantle edge carries hundreds of simple eyes; the clam partly closes when the light dims, a shadow passes or an object moves, which is a normal reflex. A mantle that no longer opens fully for several days, on the other hand, should make you look for parasites. Like all invertebrates, it does not tolerate copper treatments. It builds its shell from calcium carbonate, so it draws on the tank's calcium and alkalinity.

Water: no source consulted gives values for this species. For traded giant clams, LiveAquaria gives 22 to 25.5 °C, a specific gravity of 1.023 to 1.025, pH 8.1 to 8.4, 380 to 450 mg/L calcium, 1280 to 1350 mg/L magnesium and an alkalinity of 8 to 11 dKH.