I went to the LFS and noticed that they have several GSPs, one of which seemed really interested in me

, but the little guy has a black colored stomach

.... is this normal? He seems full of energy and healthy otherwise...no white spots or anything. I talked to the owner of the LFS, and he said that the puffers came in about 3 weeks ago and have been doing quite well.
Also, they are all about 3-4in in length, and are fully acclimated to a marine aquarium (1.022).
Thanks in advance for your input!!
