No I dont think it has a paddle. That picture is in macro mode, this guy is tiny. I dont have a sump, but planning to add a HOB refugium, could the crab go in there?
To be honest I have about 3 or 4 different crabs I have seen since I set up in September. I have pictures of most, let me add them. One or two might be out of focus though.
I have had 3 humbug's that are under 1 inch since October, one disapeared 2 weeks ago for no reason however (or could be the recent outbreak of white spot from a now dead wimple fish). I have many hermits and turbo's, plus a sand sifting star. One of my blue hermits died for no reason a few weeks back, I saw him completely out of his shell, almost like he was moving into a new shell, but there wasnt one spare. He walked about for abit before returning to his shell, he didnt move and later that night I saw a bristle worm in his shell, in the same spot where he didnt move from. I dont think any other crab had at him, do you? I put a tiny (1 inch) white goby in once, he was dead in under 24 hours, again, bristle worm found on the dead fish after.
The crabs in my tank NEVER come out in daytime, only the deep night, apart from when I first saw this one, but never again since. They are all under 1 inch, I dont think they are a problem yet with killing anything, maybe im wrong though!
Re-location to a sump or breeding trap would be good, along with getting a macro shot of him with your camera (close-up mode 
) If he is a bay guy, permanant re-location to the sump would be the safest bet, or finding him a new home with someone with a sump, would be the humanest method of "disposal". Crabs can live happy lives out of harms way in a sump indeffinately 
If he's a good guy, you can always bob him back in the display, where he can show-off 
