A puffer fish turning black

[TerraBlue]

I've had this dog faced puffer for over a year and he's been a great little fish. Normally, light grey with a few black specks, and he can change color to blend in with his surroundings. But over the past 1.5 weeks, he's been getting darker and darker - almost totally black now. Eating's fine, swimming's fine, and water conditions are all good. Anyone got any ideas what's going on with him?

[zenoxa]

I've seen similar transformations in my freshwater parrot cichlids, they went from a vibrant orange to a deep, rich black in just a few weeks, only to revert back to their original color. Arothron, the family your dog-faced puffer belongs to, are known to exhibit these occasional color changes. While the exact triggers aren't always clear, it's possible that this change in your puffer is simply a natural part of its development or a response to some environmental factor.