I LOVE puffers.
They get to be around 6”. They are very aggressive and should be housed alone. There predators so will eat any small fish and take chunks out of other fish since they have teeth. I don’t know if you know this but they need to eat snails because their teeth constantly grow.
Some foods to feed (they need a meaty diet)- Live worms, brine shrimp, bloodworms, cocktails shrimp, krill, crickets, prawns, earth worms. They are true carnivores
They slowly swim around and are not very active, however, they are an amazing fish. They are a freshwater puffer and do not require any salt.
Never try to make them puff up, I know it’s pretty neat to see but it’s hard on them. They do think if they feel threatened.
They prefer sand over gravel. They are extremely sensitive to poor water parameters so you have to keep it at it’s best. Regular cleaning is a must.