how many

Hello! I am interested in setting up a species tank for pea puffers, but I need to know some stuff! Can I keep just one? What size tank should I get? What do they eat? Can they have any other tank mates? Thank you!

I Was Thinking Of Getting A 120L Tank, And I Was Wondering What Type Of Cichlids Am I Able To To Put In And How Many Well, these are the details for my fish tank: http://www.seapets.co.uk/products/aquarium-supplies/aquariums/interpet-aquariums/interpet-fish-pod-aquarium-120.html