Atlantic Pearl Oyster (Pinctada imbricata)

Pearl oysters anchor themselves to rock with a bundle of protein fibers called byssal threads and then spend the rest of their lives filtering enormous volumes of water for phytoplankton, building an iridescent nacre layer inside their shell one microscopic coat at a time. It's the same nacre-secreting process that produces actual pearls when an irritant gets trapped inside — this species is a genuine relative of the oysters harvested for the pearl trade, just kept here for the shell rather than what might be growing inside it.

Care level: Difficult · Temperament: Peaceful · Max size: ~4" · Min tank: 30 gal, mature · Reef safe: Yes · Diet: Filter feeder, phytoplankton