I have kept Kribs for several years now, and can tell you that they are definatly an interesting Fish to keep, and easily breed in a community tank.
The last poster was correct in saying that it would be a very rare case that you would get one that would jump out of your tank.
They are mainly bottom dwellers, and love to hide in their caves most of the time, you definatly have 1 male and 2 females in there. If your tank is big enough I would provide atleast 2 caves if not more.
I have never had a problem with them pairing off and breeding, but when they are ready to, they will get very territorial, and become over protective around their breeding area of the tank.
Although they have never killed off any of their other tankmates, it is possible. They mostly just dart after them, but never engage in any physical attacks on other fish in my setup,but this could also stress the other tank mates to the point of harming them, or even dying in that sense.
So be careful if adding other tank mates, most likely if your tank is large enough, they will just stay far away from your kribs that are breeding.
As far as sexing goes, the usual tell tale sign that you have a male, or female adult Krib is their tail fin,and the coloring. While both can be very colorful and attractive fish, the females tend to have a very bright yellowish coloring to them, and are much smaller in size compared to the opposite sex.
As for the males,most types I have come across are not as colorful as the females, but thats not to say they arent as nice looking as their female counterparts, The males tend to not have much yellow color to them, if any at all, but Ive noticed more of a shade of orange on their dorsal, and tail fins.
Both of them will have red bellies when they are exited, especially when breeding, the female will have its bottom fins tucked in the make her belly apear much larger,and her coloring will get a very deep pink-purplish color.
A good sign that your female is ready to breed would be her showing off to your Male in this way, The females will even do this little courtship dance of swaying back and forth to attract the male, its very interesting to see.
I mentional sexing them by their tail fins, but I thought I'd save this for sexing Juvenile Kribs, its a bit harder to tell them apart based on color alone, since they will not show any for atleast two months.
Its actually quite easy to tell them apart even at 3 weeks old just looking at their tail fins, The female will have a tail shaped like a half circle fan, while the males will have a tail fin shaped like a Diamond,or Spade,"think ace of Spades in a deck of cards".
Hope that helps some, if you have any other questions on Kribs, drop me a line.