both male and female will get very aggressive towards your other fish, if the fish you have in the tank already are quite fast, like erm, danios, barbs then they will be ok because the kribs wont be able to catch them because they are fast, the male may even turn to the female and start harrasing her, because he wants to take on the roll of looking after the babies, he might even end up killing her, if you leave the 2 kribs in there for a while and you start to ntice them being aggressive towards each other then i would sepparate the male, for a couple of weeks, just so the babies can grow a little.