These little guys stay very small! ¾ of an inch is large for a Pea Puffer, and 1 inch is an especially large specimen. Since they are so tiny they are best kept with other nano fish, including Chili Rasboras. You can also keep them with small but not quite nano fish like Tetras and Livebearers (so long as they don't have long fins to nip, that is)!