from what i understand, anything but inverts. i really want one, but i think he should be the last addition to my tank, they can get a little agressive with new guys from what i have heard.
I have to get rid of my puffer because he killed my 2 firefish gobies 1 shrimp and bit the antennas of the other shrimp. But hasn't touched the emrald crabs.
But some fishes are different and add the puffer last but
I say go for it
My Valentini jumped out of a tiny crack in the back of my tank. He was out of the water for 8-10 mins. before we found him. I put him back in the water and he lived for a week then died. I miss him. He had the best personality. I will get another one someday.