Kribs breed very easily, all they require is a cave or place they feel safe in and they breed and breed and breed (you get the idea). The problem comes after spawning, these guys are incredible parents and will not let any other fish anywhere near their territory or fry.
In a tank your size, this could be a problem. I've seen breeding kribs take over an entire 3 foot tank to the extent that the other fish (including fully grown gourami's) were only allowed 1 corner of the tank. If they moved out of that corner the krib parents attacked, which in most cases is a fin nip or just a chase but this constant harrassment can cause deaths from the induced stress.
Kribs tend to stay at the bottom of the tank so surface dwellers like danios make good tank mates and your tetra's may well be ok but any fish that wanders near the bottom when those guys are spawning had better watch out.
Hope this helps