Cool pictures! Your spotted (brackish) puffer is not aggressive to your other inhabitants, namely your shrimp? They are such nippers in brackish tanks..
I love to add a spotted puffer to my tank, but not sure on them with coral, and my smaller fish/shrimp. I picked up a Purple Firefish for my nano, he is doing very well. I hope your pair do as well as mine is.
The puffer is well fed but even after leaving for the weekends sometimes and him getting hungry he doesn't mess with anyone.... Great personality also. He even lets the shrimp clean him.
Don't know, I don't do corals. I do know I have about 15 mushrooms that came with some rock and he hasn't even looked at them. HE also hasn't touched sponges of any kind. He has how ever nipped at some feather dusters....
