A while back I found this cool snail cruising my live rock. At the time he was about 1/4 inch. Fast forward to a week or two ago. Big (1 inch+) black snail with white blotches. He seemed to eat algae and detritus. I thought ok no harm no foul. Today with nothing much to do I decided to try and identify this hitch-hiker. Come to find out this is a predatory/scavenger whelk... I know my other snails arent supposed to last too long but I wonder if this guy helped their population decline some. Apperently whelks find snails and clams to be delicious. I have not seen this guy attack anything but undesireable items. I dont plan on keeping clams and he seems to so far do only good. I may take him out if I find otherwise.
It never ceases to amaze me what you can find hitchhiking on live rock.
I also tend to take a live and let live attitude with surprise introductions in my tank. It is important to attempt to ID them.
I think it's cool that you're planning to let this guy live. However, I would think about setting it up in its own species tank. That way it does not have a clean up crew buffet available at all times (talk about expensive taste!) and you can keep a CUC in your reef. You may be able to get the whelk to eat live clams or snails commonly for sale in asian markets.Oh, and I think you should name it "Lawrence"