should work fine, but kribs can get aggressive when breeding (of course). In my experience, a krib pair "territory" in a tank is up to 1.5 square feet. Unless you want you rams to have to defend themselves, rather than just stay on their side of the tank, either don't get a pair of kribs or make sure the tank's big enough.
Bolivian rams would probably be better with kribs than germans. I agree with Scubasteve, apistos and rams make a great combo.