My shark keeps hiding under my HOB filter! I'm thinking it's trying to use it as a cave. I've heard that they're supposed to be sort of territorial. I already have a volcano-shaped cave in the tank, but that's been claimed by my cichlid already. Plus, I think it's too small for the shark to get inside comfortably, anyway. What sort of thing should I get for him to make his lair? Do you guys have any particular suggestions? Thanks!