I would say 10g is suitable for 3 dwarf puffers as long as 1 is male and 2 are females. I keep a mated pair in a 5g with no issues whatsoever. As far as the krib goes, for sure rehome him fast, the pea puffers are all sweet when they are babies, and when they reach adulthood they generally make a turn for the dark side LOL.
