I just nuked two of these brown hairy crabs from my acros. Still got one more which managed to hide deep into my acro. The acro already encrusted so cannot take it out.
I just used my pincers to crushed them to instant death and then my cleaner shrimps had a good supper after that.
Luckily most of the crabs are the orange ones. I've another black one and white bodied ones as well. I think the difference is in the craw, if it had the small tiny craws then those are the good ones, those that had the larger craws like those brown hairy legs one then kill on sight.