Eucidaris tribuloides, the slate pencil urchin from the Caribbean and the tropical Atlantic, is sometimes mistraded as an algivore. Unfortunately, it happens instead to be a specialised, nocturnal grazer of marine sponges. A paper in 2003 found no other food sources in the gut contents of E. tribuloides, than demosponges such as Haliclona. Unless spongal growth on the 'live rock' is rife, these echinoids can only be expected to wither and die.

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