most urchins are labeled "Reef safe; with caution". They are algae eaters but may occasionally stray for a sessile invert. Rock boring urchins will bore a hole in the LR to live in and come out at night, actually most are nocturnal. Long spine black urchins should be kept with extreme caution due to their venemous spines and their habit of eating sessile inverts such as sponges and corals. The Tuxedo and Pencil urchins are excellent candidates, just pay attention to it's eating habits. The word "Urchin" comes from an Old English word which means "Hedgehog" which urchins resemble! HTH.I want one but I just have an aquapod. Are there any that would work in my tank?
Long spines get to 15+", so not them!! Tuxedos stay the smallest, less than 3", rock borers and pencils around 4".Which ones stay small?