I read in another thread that some type tend to eat coraline and sps flesh so I wont take any chance and remove him as soon as possible before he eats thru my corals.
The type you read about are the "Keyhole Limpets" and they are fairly easy to identify by the "Keyhole" at the pinnacle of their shells (it basically looks like they have peephole/bullet hole at the top, typically in/near the center of their shell).
If yours is a keyhole limpet, I still don't know that anyone has actually confirmed that they eat SPS (much like how people believe "Asterinas" - actually Aquilonstra - stars might eat their corals: they might, they might not, it might be species dependent or food availability dependent, it might be they're eating the slime coat/microalgae growing on the coral and actually helping the coral, it might be they're eating only unhealthy corals, we don't know for sure).
Either way, people do seem a lot more confident that the keyhole limpets eat coralline, but, then again, a lot of urchins eat that too, so I don't think that's a deal breaker for most people.
If it's a limpet but not a keyhole limpet, I would have zero issues keeping it in the tank.
If it's a keyhole limpet or something else that you're concerned about, you can always sump it or otherwise get rid of it, but - personally - I wouldn't be too concerned with a keyhole unless I saw it engaging in behaviors that would make me nervous (like climbing over or otherwise aggravating SPS corals - and even then I'd check for any visible damage after it's done climbing).
