My green spotted puffer was ok in my community tank for the first few months i had him. As far as i have read they need the salt more as they mature. Now he is WAY to nippy and has his own 12 gallon tank. He is always a favorite of guest that come over.
Brackish isn't that much harder. I think with him you will not have to worry with R/O water so much as just adding salt to your treated tap water. As far as salt im not a salt snob so i don't feel its necessary to buy the most expensive brand, the trick is consistency of brand and salinity. For measuring salinity a refractometer is the way to go, they are a little more expensive but they are so much more accurate so the investment is worth it in the long run. They really are not that much harder than a freshwater fish. They will eat just about anything (literally). I feed mind frozen blood worms, brine shrimp, mysis shrimp, meal worms and red wiggler worms. I have read not to feed food at the surface because they will ingest air but i have never experienced this problem, he always readily ate the fish flake when he was in the community. So thats up for you to decide.
The thing to remember with puffers is you should never move them out of the water. They will puff with air instead of water and may not be able to equalize the air afterwards, this causes them to not float properly and may eventually starve to death. So you can snag then with a net but then they should be put in a cup of water before picking them up out of their tank, move them in the cup of water, its pretty easy. And yes if your not paying attention when your feeding or cleaning the tank you might get bitten, it has happened to me a few time. Green spotted puffers don't puff up as much as some saltwater varieties, so keep that in mind, its more like their tummies expand. And it is a stress reaction so its not really healthy for them anyway. As they get comfy in their new tank they may stop puffing all together, but at least mine gets really fat when he eats, and its cute. If you get disenchanted with fish easily this may not be your best choice, i have to admit that the extra work to maintain a tank for just one fish gets a little tedious. Especially when they are small and you get that itching feeling that its silly to maintain a tank for just one fish, but then you will remember that he ate your favorite pseudo demasoni cichlid and rethink throwing him back in with anyone else. Thats about all that i know. So i hope it helps.
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