do they have the tendency to nip at other fishes fins and what not?

he doesn't seem to do it to any fish besides my blue neon dwarf gourami

he never did it to the other red gourami I gave to my gf's mom... :(
but that one was much more aggressive then the neon blue

they arent the most peacefull fish, yes they will nip at more larger fins, like guppies... is he nipping the string things on the gouramis? But they wont do much more than chase them away usualy with my experience...