It is an isopod but not a predator. These kind eat seagrasses. It is not a coincidence that they resemble catapillers. Unfortunately it would starve in a normal reeftank.
http://www.wallawalla.edu/academics...lvifera/Family-Idoteidae/Idotea_resecata.html
http://www.wallawalla.edu/academics...lvifera/Family-Idoteidae/Idotea_resecata.html