I apologize this turned into a bit of a long novel, just wanted to get all the information I had out there. Hoping this story has a happy ending!
My friend has been keeping her betta at my apartment the past 2 weeks while she moves and changed his water for the first time today. She left not long after she cleaned the tank and a few hours later I took a look at her fish and he was lethargic and bobbing vertically in the corner of his tank, fins pinned to his side. At first I feared he was dead and tapped the glass, he twitched for a moment then continued to float there. This is very strange behavior since he normally is extremely active and will react and get excited when people simply put their face near his tank. He also ALWAYS stays on his leaf hammock if he's not swimming around, so his pouting in a corner is very odd.
I left him for awhile longer not sure if I should do anything or not (his owner isn't here and is asleep) and didn't want to stress him out farther. But then he started floating up sideways, had dulled significantly in color, and getting a glazed look in his eye. I had been in the room with my friend when she was doing the water change and remember hearing the sink going and saying she was doing a full water change. Thinking she may have just used tap water I got my own betta's 'Vacation Home' (the small cup you originally buy them in) and scooped him out with enough water to fill about 20% of the cup. I filled the rest up with the distilled water I use with my betta. He layed on the bottom of the cup for awhile but after a few minutes he started swimming to the top every now and then. It's been about an hour and now his fins are no longer pinned and he is swimming around a bit. He still rests on the bottom and his swimming is a little off but he does look better...to me at least. He still is NOT a happy betta right now that's for sure.
Was it okay that I moved him? Is something else possibly wrong? I don't have anything to test the water with me. He has lost a lot of color in the past couple hours and if I look close he has a 'film' over his coat. Could it all be from using tap water? He was perfectly fine pre-water change. I'd like to do anything I can to help the little guy, he's a happy little dude (would also be nice to not be accused of killing my friends fish while trying to save him ^^;).