ey0 b0sses, i made a post a while ago with(i think) a lot of good information on it. here's the link to it: http://hamsterhideout.com/forum/topic/147792-hermit-crab-help/?p=1619549
anddd i just realized this is a 1 month bump, sorry
to answer your original question, hermit crabs can be housed alone if you're giving them all the proper care, but it's generally just a lot better to house them in social groups. they feel safer in larger groups, and if you provide enough shells of the right size there shouldn't be any issues with crab fights. VERY IMPORTANT NOTICE: sub HAS to be at least 6 inches or the depth has to be 3 times the size of your largest crab, because if crabs are molting in substrate any less than that surface crabs can smell them, locate them, and then eat them while the crab is molting without its hard exoskeleton.
sorry about what you had to deal with, i dont want to choose sides but nevertheless there was no need for the other member to answer like that