GSPs and Planted Tanks

Because of the high s.g. Green Spotted Puffers require, it's difficult to house them with live plants. Most plants will die off as the amount of salt in the tank increases. There are a few plants that are known to survive and sometimes thrive in brackish waters.
Links to lists of brackish plants:
WetWebMedia
Article by AMS
Seagrass
PlantGeek.net

It's also important to remember that Green Spotted Puffers are Omnivorous, and may see all plants as a tasty snack. When they eat plants, they take tiny circular bites out of them.