Hitch hiker

[Nano]

Cant get a picture if I tried this little thing is so fast and it moves all around inside my LR, but he stays on the rock with my Zoas. I have only seen it once but my wife just phoned me saying she tried to get pictures, but he is too fast. She says it some what resembles a beetle, dark colored and about the size of a stomatella snail.. I'm not sure if I should be worried? I just noticed it about 2 days ago, and there is no visible damage to anything. Any thoughts? I know its hard to say with out pictures.. sorry guys