Hi, I just inherited a green puffer from my roommate who was moving! All it does is sit on the floor of the tank. The fish does not seem to want to eat and his(?) mouth is open all the time. I read that this might mean that their teeth are overgrown, but I can see the mouth opening and closing so I don't think it's the teeth. She told me that the water was fresh, so I am adding some salt (instant ocean) according to the directions to create a brackish tank on the puffer forum. I am still in the process of doing that. The water has a very high PH, and zero ammonia. We do (well, will do) a 50% water change every 30 days. He/she eats frozen bloodworms, frozen krill and clams on the half shell. OH! And snails once a week. Gold ones.
I'm worried. I don't want him or her to die!!! Oh, and he or she is really small, and skinny! All of the pictures I have seen have fat fish in them. I know she took good care of him/ her. (How do I tell the gender so I can stop doing this.)
There doesn't look to be any sign of parasites, but the belly does have some grey on it's edges.
(I also posted this on The Puffer Forum)
Hey, welcome! You don't say what kind of puffer it is. Green Spotted? How big is it? You need to raise salinity very slowly, or you will kill the bacteria in your filter, and create the tank to go into a mini cycle, which will be deadly for this guy.
You should do water changes more often. Grey around the belly can indicate stress, it can be that he's sleeping. If he is skinny, get some Prazipro (for internal parasites) and add to water, or even better, soak his food in it, with some garlic extract (that will encourage him to eat it). You also need to know your water parameters. There should be no ammonia, no nitrites and your nitrates should be under 20ppm.
You'll get some help on the Pufferforum, too. I would feed pond or small ramshorn snails (the size of his eye) to keep his teeth worn. If he's never had snails to eat where he crushes the shell, over grown teeth could be the problem. How long had your friend had this puffer before you?