My puffer looks very healthy, but within the past few weeks he's slowly eating less and less. Today he wont eat at all. He's also a lot less active. I purchased him from craigslist about 2 years ago so I have no idea how old he is (he was already about 9 inches at time of purchase). Could it be that he is dying from old age? I have 2 other tangs and they are still going strong as ever.