I have a porc. puffer in my 65 and he has plenty of room, I know I will have to upgrade when he outgrows it though. I have to tell ya, that fish is pretty neat! I have never had a fish with a personality like his.
NO, they don't. Honestly, I think the porky would be fine in your tank for atleast a couple years.. they don't grow very fast in my experiences... if you don't mind getting rid of him when he gets too big, you'd be fine.
You can easily keep a porky in a 75 for a couple years for sure. They dont need a ton of room just good water. If you bought a 2-3 inch porky I would say he could be kept in a 75 for 3 years maybe more.
get hovercraft boxfish.....they have the personality of porky.....but grow to mere 5"....perfect fish to have in 75...also another plus is they're less likely to release toxin like other boxfishes.....no need to worry about that.....there are two hovercrafts available.....Lactoria fornasini and Tetrosomuc gibbosus....I have one in 55, and he'll do anything to attract my attention......most personable fish...IMO....I highly recommend it to anyone who do not have aggressive/nippy/fast-swimming tankmates.....
get a porc puffer. They are amazing, I had one in my 75 gallon for a little over a year and he had plenty of room, he passed away recently due to power outages and storms but they have great personality and are very fun to watch