I started a hospital tank today which is 2 gallons so I could more effectively treat my fish for minor fin rot (he was bought this way). My water quality is good-Ammonia, nitrates, both 0ppm and ph is 7.2. I acclimated the fish for an hour in a betta cup the temp was 78 he is used to 82. I had waited for a few hours before putting him in and that was as high as it would go.
After releasing him he just went to the bottom and stayed there. He normally will rest on leaves at the top. He was not swimming to the top very well so I lowered the water level to about a gallon. He eventually started laying his side and it didn't seem like he was going to be able to surface so I went ahead and stuck him back in the cup. I lowered the lights and added a little stress coat. I could not figure out why my heater was not going to the normal 82 and I had left it uncovered it's an extra large glass food container so I was going to use plastic wrap instead of the airtight lid.. So now we're up to 84. (The warming up was slow)
I have changed my water as suggested and never had this reaction before. There is nothing in the water but a 1/2 teaspoon of salt. The water was aged with Prime for at least 4 days plus it had Jungle Aloe slime coat.
I think I've done all the things I can. If you have any additional suggestions let me know. I plant to leave him in the cup overnight so I know he can breathe.