First things first…
is this tank a new setup, or is it an established tank?, either way, don’t get the GSP right away, if you add enough aquarium salt to turn the water brackish in an established tank, you’ll lose a good amount of your nitrifying bacteria, your best bet is to re-cycle your tank with some hardy fish like mollies (the plain ones), mollies actually do better in brackish than fresh water, they’re not as prone to fin fungus, puffers don’t tolerate ammonia spikes very well, and could be killed in a re-cycling tank
apparently, the GSP is brackish only in it’s juvenile stage, once it matures (2-3 years or so) it needs full marine conditions
my GSP lived a couple of years before he came down with some form of gas pocket on his side that kept him floating at the top of the tank, it was hard for him to eat, and the gas pocket evaded my attempts to cure it both medically and surgically, so i had him put down, sad really, as he had a definite personality and was so tame i could hand-feed him…
that tank now houses 6 baby Dwarf Puffers, straight freshwater fish and they won’t get any bigger than 1", dwarfs are social and have the same inquisitive, interactive personality as GSP’s
your water settings look fine, if a bit on the high brackish side
puffers are carnivores, i fed mine a staple of freeze dried krill, other foods he enjoyed were;
ghost shrimp and crawfish, he’d actually hunt these, Maylasian Trumpet Snails were a constant source of live food for him as they are livebearing snails, they’d hide in the gravel until they were big enough to be snacks, for a special treat, i’d very occasionally give him small earthworms
puffers are extremely messy fish, they generate a lot of waste, minimum tank size for a single puffer would be a 20 long or a 30, puffers tend to orient horizontally, so tank length is more important than height, a 40 breeder would be luxurious accomodations, your 25 should be fine for a single puff
make sure you have a decent power filter and heater, i use a Penguin Emporer 280 BioWheel filter and an Ebo-Jaeger 100 watt submersible heater in my 20L, you may want to step up to an Emporer 400 and perhaps a 120+ watt heater
salt-resistant plants like Java Fern and Java Moss would be good to have as well, to keep the nitrogen cycle running properly
use Instant Ocean brand salt, it’s the most consistent, i’d assume you already have a decent hygrometer, when you do water changes (50% weekly) you don’t need to add as much salt, as salt doesn’t evaporate, just the water, and never add aquarium salt directly to an occupied aquarium, mix it in a bucket outside the tank
tankmates; well, it really depends on your puff, some puffs (like mine) were fine with tankmates, he had 3 mollies (the plain variety) and 3 bumblebee gobies as tankmates, and he really didn’t care about them either way, he was more interested in interacting with me, crawfish and ghost shrimp were considered snacks, so don’t plan on any invertabrates as tankmates, they’ll end up as snacks
Puffers are great pets, yes, i said pets, they’re one of the smartest fish in the aquarium hobby (Oscars are another smart fish), your puffer will recognize you and beg for food, follow your movements around the room, i’d even say that they have emotional states, just like terrestrial animals…
for example, when i got up in the morning, Zaphod would be happily swimming up and down in his tank, begging for breakfast, i’d hand-feed him a few pieces of krill, and go to work…
when i returned from work, before he saw me, he’d be resting on the gravel, gazing down at it and looking depressed, his colors would be dull and gray, as soon as he saw me, his colors would instantly brighten up and he’d happily swim around his tank, following my motions, watching me, and begging for more food…
i really miss him, he was an awesome fish, luckilly, the dwarfs seem to be just as personable, they buzz around the tank, intently inspecting everything, and they’re just starting to learn that “The Big Hand From The Sky” gives them treats
puffers are some of the best aquarium fish, they’re not hard to keep per se, they just have rather specific requirements
