Pea puffers need slightly soft water. The hardness level should be low to moderate at 4 to 10 dGH. Pea puffers can tolerate higher alkalinity, however, they thrive best in softer water.
Aside from the alkalinity, you also need to pay attention to the water’s temperature and chemistry. Pea puffers prefer warmer water with temperatures between 75°F and 80°F (23.8° C and 26.6° C).
Meanwhile, the pH should be neutral at around 6.5 to 7.5. Lastly, the ammonia and nitrite levels should be zero, while the nitrate level should be below 20 mg/l.
Additionally, while pea puffers are hardy and able to tolerate a wide range of water conditions, they’re rather sensitive to changes. Maintain the water parameters as best as you can.
To do this, install an adequate filtration system in the tank, monitor the ammonia levels regularly, and change 25–50% of the water weekly.