Your tank is 180L? I wouldn't do it in anything under 220. Kribs tend to hold a large territory when breeding, although it is more about the footprint than the volume. I had a pair of kribs and a pair of rams in a 45 and they killed the rams the morning they decided to breed. If you do put them together add lots of wood piled on itself (more than you would probably want; no less than 10 caves) and add a ton of plants. Try and make a visual barrier between the two sides of the tank, I find that visual barriers work the best for mitigating the amount of fighting.