Chances are it's fine, I would keep an eye out for it again. Watch your corals, if it's hanging out on them then I would pull it. If you see it again and it's just in the sand or on the rock or glass, I wouldn't worry too much. But if you don't like it and can grab it, pull it if it makes you feel better. I use my turkey baster to suck critters out. It seems to work better than tongs, a net or paper towels.
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