porcupine reqiure a big tank for it to grow, some ppl said at least 55, but some said at least 120gal. no HOB filter is need, just a skimmers.
I had one before in a super small tank 46gal, I bought it when its like 2inches and 1 year later, it became 5 inches. I just use the regular night that usually come with the tank.
its a messy eater, so every week or 2 must do water change.
2~4inches should feed everyday
4~6inches about every other day
6+ feed once a week will be fine.
I would say at least give it a 75 gal if possible, if 50 is the only tank u have, u can try, it won't stress that much if u play and feed it.
mine was swimming happily all day. (u will know if it stress, it tail will put a side and won't open, the body color will change to super light brown, mine change to dark brown when its trying to poop LOL)
No snails and other invert should be with it IME
my porcupine killed 3 cleaner shrimps, 2 yellow sleepers, 3hermits (I was a newbie at that time OoO)
hermits r hander to kill, so if u get some bigger ones, they should do fine.
OH, never use a net on porcupine, they will puff and you will be crazy to take it off the net.
Porcupine is fun to play with, well at least mine was.
I m the one who usually feed it, so other people walk by, it won't bother to look, but if I walk by, it would swim to the top and swim really fast to showed that it wants food, XD really funny face.
feel free to ask if u have any question about porcupine, I will try my best to share my experience.
I would suggest green spotted puffer too, they r in FW or brackish in LFS, but they can easily adopt SW. I have 3 in my SW tank now, and its best for them in SW when they grow bigger (younger transfer to SW the better.)