I love these guys I've had them for years they get huge, biggest one is 8 inches. They need lots of room when kept in pairs. They are really slow and love to uproot plants. Fish beware they are armed and extremely dangerous. Keep them with fast fish if they get a hold of one its over!!!!
Mine was probably about 6-7 inches from tail to claw. Do not keep with fish or plants unless you don't care if they get eatten. Mine didn't mess with plants as much but any fish I put in it got eatten right away. I put in a betta without knowing how aggressive they were. 15 minutes later I look back and the betta is missing all its fins.