Facedown Gold fish

Question

face down gold fish   On firday i took my comet gold fish out of my 10 gal tank to make room for my other fish, so i put him in the pond in the back yard he was fine for 2 days. it is now Sunday i went to check on him and he was on his side still alive moving his mouth and fins a little.i put him in a 1 gal tank brought him in and was taking a little warm water from the 10 gal tank to warm him up slowly. i did this for about 2 hours, he returned to normal so i put him back in the 10 gal tank,he was fine for about 3 hours then he went face down not moving fins but still breathing. Whats wrong with him?
P.S. I also did a 2 gal water change and added salt

Answer
Hello Ryan!
Well the reason/cause of this is most likely caused by the sudden change in water temperature. Also if the pond water was dirty then it would be sick. Another reason for this is that it does not have any tank mates with it. Gold Fish like to swim together and are often very timid. Since you changed the environment multiple times, temperature changes, loneliness, and stress could have caused this. Try getting the API Stress Coat because it can remove up to 40% of stress (scientifically proven).

Hope this helps! xD
~Sam