BeavisMom62
Aquarium Advice Freak
you need a hydrometer or refractometer. GSP can get big and require a 25-30 gallon for just one. When they are fully mature they are usually saltwater fish but should be kept at least at a high brackish. you puffer is still young and should be kept in low brackish. you are probably better off returning it and getting a figure 8 puffer. they stay small and are brackish for life. you could be killing your puffer by dumping him into saltwater and not brackish. you need to do some more research.
Ha, a pet store did that to me once. I knew that I waned a F8 but they gave me a GSP and told me that it was the same thing. Since I wasn't too sure about the markings, I bought it, brought it home and only THEN did I go onlineto compare the markings and realized I had a GSP. Since I only had a 15 gal tank, I had to take the little guy back. I ended up giving up on puffers. I just couldn't seem to get the SG right in that tank. To me, it was too much trouble so I decided to stick with FW. Leave the water out overnight to mix the salt, but then the water was too cold (didnt have an extra heater), add warm water to the bucket to get to the correct temp, which threw off the SG, add more salt, whoops, SG too high, add more water, whoops temp is off......whew! Gave it up.