You can keep up to three pea puffers in a 10-gallon tank. Despite being tiny, pea puffers require plenty of space to accommodate their active and territorial nature.
A single pea puffer requires at least five gallons of space and each additional puffer needs three gallons of extra space. However, this equation only takes pea puffers into account, so it only applies if you’re keeping a species tank.
If you wish to keep other species in the tank, make sure to account for them as well. Avoid overcrowding the tank since it will cause the pea puffers to become stressed and aggressive.