Actually, I just logged on to post an update. The spots on the tail are actually algae/ditritus on the tank that can be seen through its tail.
Update -
Well, I have good news and bad news. Anyway, as Leopard_babe had mentioned, that puffers are nocturnal - so I decided to spy on the puffer at night with the lights off. What I realized is while the dog face gets ready to sleep, the porcupine turns into a predator. The procupine was actively looking for food.
Earlier in the day I had added a few chromis. The porcupine was all over the tank chasing the chromis. When I saw that I decided to hold a squid tentacle in the tank and mimic a swimming motion. The porcupine showed interest in the tentacle and eventually ate it. Yes!!!
The bad news: when I checked on the tank this morning, I was missing a chromis. I can't find it anywhere in the tank. They way the porcupine was after the chromis, I'm sure it ate one. Bottomline, it looks like my porcupine is mainly interested in live foods. Especially at night when the lights are off.
Before I wanted to do whatever I could to keep the porcupine alive. Now I'm thinking about giving it up to a LFS. By the way its actiing, when it gets bigger it will eat more fish. I guess this is a reason some people end up owning multiple tanks.