LOL when I started reading I was gonna suggest Cory's lol....but you remembered it
Here's a good quote on your kribensis from a very reputable source
"Good tankmates include small characins, barbs, danios, rasboras, Corydoras
, gouramis and Loricariids."
I hope this helps you. The Cory do act less skiddish in larger groups yes. That said thou if you provide some hiding placed (caves, plants...) and house a school of 6 that would be just fine.
Or what about kuhli loaches had you given them any thoughts (needing ph 5-7 and KH 5-15 if you have that range).
Only last thing for the size tank & bottom would be shrimp, but I am very sure you kribensiswould like that snack
For the top...others then hatchetfishI couldn't think of no one neither right now sorry.