My name is Fi ... I have a lovely little GSP called Bryan - no idea if he is a Bryan btw he could actually be a Bryony!!!! I have had Bryan in the fish family since lockdown weekend in March. Bryan wasn’t an intended addition, I didn’t even know you could buy puffers!!!
I upgraded my fish tank for a new to me 300 L tank at end of January ( due to OH buying me a loach on a whim last year) and moved my fish family from their 65 l tank after a perfect fish-less cycle at the end of Feb, I added a few new fish mid March and was happy to then wait to see how everything settled.
During that time I broke my ankle and had to rely on OH to run me around or go and buy plants/food etc .......It was during a trip to one of our LFS ( chores for me) that OH and our Grand-monster spotted Bryan and thought he was cute and would be a great addition to my tank! ( apparently the 5yr old grand monsters idea ) Due to not having a quarantine tank set up Bryan was added straight to my tank.........Apparently the guy at our LFS had told OH that Bryan didn’t need any special requirements, would be fine in my set up..............Bryan is the 3rd addition to my tank bought on a whim by my OH and Grand-monster.
Google has been my best friend since I introduced Bryan and Bryan is now living in my 65l tank on his own which has been going through freshwater change to brackish water since May .......Now I have found this forum I am off to do more research and ask questions.
Thanks for allowing me to join
GSPs, like many puffers, have big appetites, and are very territorial. As far as I know, GSPs can thrive in brackish, but love marine just as much. My word of advice, be careful with tankmates. The puffer can either kill or be killed, depending on the fish you keep with it. Also, always keep up with the water changes, water changes, water changes! Puffers are not forgiving like other fish, and will quickly go downhill if not monitored. 
Puffers...