HCA: Hermit Crab Association

So, digging around in my shell pile, I found this wonderful shell that would probably make one of my crabs happy. It's a good size, and it's smooth.

But the reason it had disappeared was because the place I got it from, wherever that was, had it decorated with permanent marker. Like a painted shell but just very lazy.

I want to get the marker off and I've tried a lot of stuff, but to no avail.

Does anyone have any recommendations, preferably safe for hermit crabs?

Try soaking it in rubbing alcohol then boiling it to get the alcohol off??

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Shells are porous, there is really no way to remove the sharpie without making the shell unfit for crabs to live in.