Lost my female Nigerkento4 Red Krib, Neera, yesterday to aggression from the male. I'd tried rearranging the tank, but no luck. Took them out for a clean, and she was looking really rough at the back of the tank. When I checked on them in the bucket, she was on her side, struggling to breathe, and he just wouldn't leave her be. I tried to revive her, but sadly, she passed away last night.
Thinking of selling the male now and just keeping the Ocellated pair - they seem okay for now. By the time they're the same size and age as the Nigerkento4 Reds were, I'll have a separate tank to split them if aggression becomes an issue.
RIP Neera