A quote from an article on the puffer forum
"the popular Dwarf Puffer (Carinotetraodon travancoricus). This Puffer stays small, only reaching 1-1.5 inches. One thing that makes these Puffers unique is that it is easy to determine their gender once they have sexually matured. The males stay smaller and develop a dark brown vertical stripe on their stomachs. Females are usually larger and lack the stripe (Ed note: Males can always be distinguished by their colourful cheek “wrinkle” patterns). If the proper tank is provided (that is, one that supplies at least 2-3 gallons per Puffer), is heavily decorated and has more hideouts than there are Puffers, then keeping 2 or 3 females to one male often works well. In fact, under these circumstances and with proper diet, Dwarf Puffers will often spawn. Dwarf Puffers have been kept successfully with Otocinclus algae eaters. There has also been limited success in keeping Dwarf Puffers with different species of shrimps, such as Amano, Cherry or Ghost shrimp. There is always a risk with shrimp that some Dwarf Puffers will decide that they are food and will eat them."