I got two GSPs about 2&1/2 months ago. One died shortly after but the second limped along until last night. The first sign of trouble was one of the gills clamping shut. So I treated for gill flukes. Nothing. So after a while I treated for internal parasites. Things got a little better. Then the symptomes appeared again. I treated the water this time with CopperSafe. The fish then did well for 3 weeks and then stopped eating, twitched, lost color, and became sunken and emaciated. I did a 50% water change to try and get out the last of the copper (I had done regular water changes before) and treated again with JungleMate. The fish began eating regularly but did not put on weight. Last night I noticed a bulge just off center of it's belly, today it was dead. I have a 20 gallon tank, nitrate, nitrites and amonia are zero or barely readable, ph is 8.1, salinity is 1.017, temperature is 79 - 81 dgrees F. I have a second puffer that I got last week and do not want this to happen again. Can someone please tell me what went wrong?