Wierd things happening in my tank....

[Pisces]

I've had my tank for 2-3 years now, but I still feel like an amateur....it's pretty much a 'fish only' tank, with the exception of some fairly recent (few months or so) star polyps.

I have a Regal Tang, and he behaves differently than I would expect him too.....to be more specific, I've caught him hauling snail shells around, nipping at starfish, and even at my spiny urchin! I had one previous to this one that behaved similiarily, so I took him back to the store. That one even went as far as nipping at my brittle star and cowrie.

Also, my spiny urchin has white bands around it's spikes.....a friend of mine told me it was a zebra urchin, but I don't think so. When it was new and little, it was all black. Is this normal?