I have one fancy fantail goldfish in a 20 gallon long aquarium. All water parameters are normal. I feed her granules soaked in water first, and supplement that with peas a couple days a week. Over the past week or so I've noticed that her stomach looks more swollen than usual. Also she is having a hard time swimming all the way to the bottom of the tank. Normally she can get all the way to the bottom and sift through the sand but now her bottom is floating up so she ends up with her nose pointed to the bottom and can't stay on the bottom for more than a couple seconds, but otherwise she is swimming normally and isn't floating upside down. When she sees me she swims to the top and she does swallow some air. There is plenty of oxygen from the filter and a bubble wand so lack of oxygen is not a problem. I am also guilty of over feeding her at times because she is such a beggar for food. I know that these symptoms could be a sign of constipation or swim bladder so I raised the temperature in the tank from around 68 to 74 and fasted her for two days. she seemed to improve a little and didn't look quite as bloated . Then I gave her one pea a day for two days after that. Now she's right back to floating bottom up. Seeing as though she seemed to get a little better from fasting I'm wondering if I should start to fast her again but I don't want to starve her. I don't know how long I can safely withhold food without any detrimental effects. Another question that I have is what is the difference between swimbladder and constipation? I would appreciate any thoughts or advice as to what I should do.