I had my Kribs breeding in my 4 foot tank and they basically claimed the left hand side to themselves, although they did allow a trio of corys i have to stay down their end, rarely chasing them.
From what i can tell, their agression doesnt involve any biting/nipping and simply relies on intimidation.
Your fry should be ok in your tank but of the 40/50 that start out i would only expect half a dozen to reach maturity. Good luck
I have Bolivian Rams in my tank too, with the Kribs they got along fine, but they are relatively young and did end up getting pushed around themselves a little.
In the end i got a bit annoyed with how agressive they get and how often they spawned, it was a little too much, so i've since moved them into my Tiger barb tank along with the 5 Juvenile kribs i got with the first spawn. Spawning Kribs is fun the first time around, amazing to watch, but it kind of loses its appeal quickly, as there isnt any real effort or trick to get them to spawn and you just end up with loads of fry which you have to get rid of, which around my way is quite hard as every lfs has loads of kribs already!
I wouldnt recommend Kribs go into a tank thats under 4 foot long if you want to breed them, as mentioned before, their demands for space when they move their fry around is quite high. Im hoping they dont actually spawn in my 90 litre, i'll be a tad annoyed if they do and i'll be looking to rehome them. bleh.