What about fish? I new they had a vad sting and not to pick them up with bare hands. I had a couple years ago and can't recall any issue. I just noticed him at that same spot on my clam.
Conus regius is known to consume polychaete worms (bristle worms). I suppose if you don’t have any worms in your tank, there’s a chance it would go for something else, but I personally don’t know for certain.
Also, just in case anyone else reading this is unaware, cone snails are highly venomous, and while Conus regius specifically is unlikely to kill you with a sting, it could still cause some rather unpleasant (but thankfully - from what I’ve read - relatively short-lived) symptoms like in the case discussed below. Please note, stings from several other conus species (typically the ones that eat fish) would be likely to kill you, so handle any conus genus specimens very carefully.