Cool, that's going to stress your crabs out a lot. They won't be in their new tanks thinking about how much they miss the other crabs, they'll be grateful for the room and for the privacy they have now. They won't be sitting around going "Hmm, wonder what _____ is doing right now?" Moving them from tank to tank every week will stress them out to the level they were back when they were all in 1 tank, or even to the level they were back in the pet store. Crabs like to have control over when and where they move to, not be moved around all the time into unfamiliar surroundings. Also, moving crabs from tank to tank (even if it's to ISO them) will make them put off their molts, which, if they need to molt, the buildup of the hormone that makes them put off molting can eventually kill them. That's also why I don't move molters into the ISO if they aren't surface molting - it makes them stop molting until they feel safe in their new surroundings, so why would I do that?