It was in freshwater and only about 1.5 inches. but its belly was white and it looked happy as it swam up and down the tank.
GSPs can and will do well in freshwater for a long time, certainly many months, perhaps even a year or so. So the fact it is a freshwater aquarium shouldn't in itself be a problem assuming that the water is clean (zero ammonia/nitrite) and that the water has a high level of carbonate hardness (to inhibit pH changes).
I just put my GSP in my 20 gallon tank. It has a very low salt level, but i thought iu would have the little guy adapt slowly.
Absolutely no need to worry about the fish re: salinity changes. This species can adapt to big changes in salinity virtually instantly. Your filter bacteria are different. I'd make sure that the salinity was around SG 1.002-1.003 now, and leave it running thus for the next few months. After 3-6 months you can then raise it to SG 1.005 by a series of water changes across a few weeks (i.e., do weekly 25% water changes, adding SG 1.005 water each time). Once you're there, you can decide whether you want to maintain the fish at this low salinity or at a higher one.
Now that it is in my new tank, he is active, but his belly has turned spotted black. I am worried about the little guy. Is it just because he is afraid or is the tank messed up?
Don't read *too* much into colour; all puffers change their colours along with their moods, and the dark belly doesn't so much mean sickness as it does stress. If the fish is swimming, breathing, and eating normally, don't worry too much about colour. Do of course test the water for nitrite or ammonia.
The temp is good and the salt should be good, but i am new at fish and am not exactly sure on how to check the ammonia and Ph level stuff like that.
OK, your three essential tests here are nitrite, pH and salinity. Ammonia can be substituted for nitrite, but you don't need to do both; one or other is fine. Both nitrite and pH are measured with test kits. For nitrite, you want a ZERO reading. Anything else is bad. The pH needs to be in the basic range, ideally 7.5-8. Salinity is measured indirectly, using specific gravity (water density). You need a thing called a hydrometer for that. Cheap floating glass ones are fine. You're aiming for SG 1.002-1.003 initially, about 5-6 grammes of marine salt mix per litre.
Should i worry? i really want him to live.
Some "worry" is good if this is all new to you, but reading around the topic and using your test kits/hydrometer to check water conditions are much more useful than fretting! Do look over my Brackish FAQ for stuff on brackish water fishkeeping, or better yet, buy/borrow my book!
Cheers, Neale
