Kribs are fine until they breed, which they will if you get a male and a female (well breed or kill one of them). Once they have babies though they will take over your tank like little psycho's, if another fish so much as moves a muscle they will chase it away. That's my experience of them anyways, my Kribs now have my 125l to themselves and their babies, who i expect will be next on the hitlist once their next brood hatch.
Other than that though they're beautiful wee colourful characters with lots of interesting wee quirks, like digging holes and forming massive mounds once you've just nicely re-scaped the sand in your tank etc.
Hmmm.......I'm beginning to question why I have them now.......