Green Spotted Puffer Fish sleeping behavior?

Question

I have two Green Spotted Puffers in a 60 gallon tank. They are the strangest fish I have ever kept. Very curious and easily entertained, they explore the tank all day looking for brine shrimp that fell to the bottom. But every night at around 9:00 I go to turn off their light and can't find them. I look around the tank and they will be behind a large rock curled up in little balls laying on the bottom, like a dog or something. Is it normal for them to do that? Are they stressed or something?

Answer 1

How long are you leaving your lights on?  If they feel it's time to rest, they certainly will.  As you noted, they do their fair share of swimming, and will tire, especially if they aren't getting a whole lot of food, or if the water is an extreme temperature.  As long as they're otherwise healthy, I wouldn't be at all concerned.