The Puffer Forum

I have a 29 gallon tank, with 2 cichlids and 1 plecostamus. I noticed today that it is only when i have the lights off his belly turns white, but when i turn it back on, after a few minutes it starts to turn black. i threw 5 ghost shrimp in there and they are still alive and well.

Please help, I just bought my ceylon puffer from a LFS and he was fine the first 2 days, now his belly is very dark and black, does that mean he is sick?
I just bought my tank 1 week ago, and cycled it with "Cycle", all the other fish are fine except for the puffer.