Cage mate barbering

Does anybody have any tips on preventing cagemate barbering? They have a big cage and Ive provided lots of hammocks and chews but one of the young rats is barbering the hair off his brother's snout.
I let them out for half an hour when im not in work too, but that doesnt seem to be helping.

Anything i can do?

please read this, the ratguide is a vet approved medical site for rat owners .... it contains some suggestions http://ratguide.com/health/integumentary_skin/barbering.php

I was never able to stop any barbering but I figured, as long as the rat is not being hurt in any way, I allowed it and eventually it did stop.