here's some info, borrowed from another site. think it's pretty accurate, cause the undersides of the LR it grazes on is bare"Orange Frilly Limpet - Lucapina aegis
Can you ID this?
<yep>
It's in a reef tank. Is it bad or good , Friend or foe..
<foe... as most limpets ultimately are. They are somewhat indiscriminate feeders on benthic life forms. The brighter colors are usually a giveaway (noxious and freely predating on desirable reef life - perhaps corals or sponges). Its best to remove this species and a tank without reef invertebrates."