All hermits at some time in their life get jealous of their snail counterparts shells. Their idea is the snail must die in order to get the shell. All hermits will do this. I have kept Zebras and they are my favorite hermits except for maybe the new Lightning Blue Hermits that FFExpress has under their Collectors Corner (is acutually LiveAquaria now but I still call it FFE). I had Zebras until my Undulated Trigger got to them (they didn't close as fast as the Blues so paid the consequence). I felt bad when I saw their little shells, and want to get more but I currently have a puffer or multiple triggers in all 3 of my marine tanks so will have to wait for a little while till I set up a new marine tank. I didn't find them to be aggressive. Out of curiosity, why are you trying to stay away from Blues? These are the only ones that have a success rate since they hitch hiked to the new 209 and are currently Queen Trigger play toys. Fornuatly for the crabs, they are smart and the Queen still has A LOT of learning to do.