Pea Puffers are a little nippy towards their tank mates but mostly because they are always looking for potential food sources. They will eat most invertebrates but this is more being predatory. Pea Puffers can be aggressive towards each other, however. Especially males, which are territorial and may fight for access to females. Fortunately, they are so small that you can still keep multiple males so long as they have space to form their own territories.