puffer quarantine and cupramine

i purachsed an baby porci puffer and i drip acclimated him for an hour. i placed him in and fed him. he was eating mysis like a champ. the next morning, there was a small bacterial bloom. i got scared and did a 6 gallon water change. the tank is 20 gal. the puffer is 1''. Then i saw icy all over his fins and he is sitting on the sand breathing really fast. i have a 1 gallon fish bowl with a air pump. can i fill the fish bowl with my bio cube 29 water and take the puffer out of the 20 and place him in the fish bowl with a heater and air pump and some hideaway? i will treat with cupramine. do i need a larger tank, or what else will be better. i feel really helpless. he looks like he's gonna die soon