krib space

I'd go with one pair. They can get mean towards each other if they decide to breed.
 
That's not to say you couldn't have other fish though
2 kribs in a 30 gal with adequate filtration is definitely not overstocked.
 
Yep, one pair. One pair will defend a minimum of a one foot radius (all directions). When fry are being tended to, this increases to a minimum of one foot from the location of the brood.

I would keep fish that can quickly swim from the darting of the krib parents.
 
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