A puffer is a flesh eating predator and will/can eat soft corals and any crabs/inverts you keep in the tank.
They are a neat fish, but are usually reserved for a predatory tank with other fish like lionfish, eels, groupers, tuskfish, etc.
I have seen that you were looking to keep corals, if you still are its probably best that you avoid this fish, it is not reef-safe.
If you do end up with it, make sure you feed it a varied diet and not just krill. Over time krill can wreak havoc on their digestive system and cause them to starve themselves to death. I know someone that was able to overcome this, but it was touch and go the whole time and I am sure that he would agree that its best avoided.