Lol trust me, that is not fighting, they are just trying to find food and/or cleaning the other crabs shell or just decided he wanted to go on top of his friend there. You will know when they are fighting. One time my zebra pulled a hermit out of his shell, and then decided he didn't like the shell anyway. Another time 2 were locked together, opening of shell to opening of shell. I had to take them out of the tank to pry them apart.