How can you tell the sex of green spotted puffer fish and how can I breed them if I wanted to?

I have a few green spotted puffer fish, which have a brownish color and green spots. When they feel scared they can puff the body up to look like a pourcipine. I would like to know how to tell the sex of them and how to breed them. I don't think it is by the fins either. Any info will help, thank you!

Sexing and Breeding: Sexing is difficult as there are few visible differences between male and female fish.But normally the males will have brighter colours than the female.The female will have less green and more brown but there are no other differences.Breeding is very hard and rare you can't make it happen it just happens by suprise.The signs that they have started breeding are:spawning occurs in brackish water.The eggs are laid on a substrate or stone,and guarded by the male. Hatching takes about a week.Heres some more things:They need a good amount of room, I suggest a 200+ liter tank.Green Puffers are always hungry, and they will eat themselves to death.They can grow large and live a full life, if you take care of them properly. Green Pufferfish are brackish, so they need salt, such as Instant Ocean, not aquarium salt. Their diets should consist of bloodworms, ghost shrimp, and pond snails. The snails are to help keep their teeth from growing too large. Also, Puffers are fin nippers, and only should be kept with other Puffers, African Cichlids, and sometimes Molly's. GOOD LUCK!!