Porcupine and Dogface puffers are usually very lazy by nature in comparison to say the Spiny Box or Stars and Stripes Puffers. A couple things that will affect your Porky's activity level are:
1.) Water quality. I noticed a huge difference in activity once I started adding supplements like Ca and Iodine. I thought set-ups without corals didn't need it, but then realized ALL seawater contains these elements - even where Puffers are. Always try to mimick natual water as close as possible regardless of what is in your tank.
2.) Lighting. There is a reason Porcupine Puffers have such HUGE beautiful eyes - they are a deep water fish. Therefore bright or intense lighting can cause them to hide in shaded areas all day. Once I switched my lighting from 50/50 to just one 1-watt LED moonlight my Porky was out all day swimming. Intense lighting is also a possible cause of Porky's getting cataracts as they age.
3.) Feeding. Porky's, like most puffers and fish for that matter, LOVE to eat and don't remember stuffing their faces 5 minutes after they are done. It is very common for poeple to stuff their puffers and keep them very fat (since they beg like dogs) - which causes them to rest on the substrate to digest. hence the more you feed, the more rest is necessary. I only feed my Porky twice, maybe three times a week and he is very active.
Murray BMF is right, the first sign somehting is wrong a puffer will stop eating. Good Luck with the little lazy guy
