Welcome to AA! Just a few questions so we can help you out
(*)what are your ammonia, nitrite and nitrate levels? And do you haves test kit to test for this?
(*)when was the tank set up?
(*)has the tank been properly cycled?
(*)is there decent surface agitation, or an airstone to oxygenate the water?
(*)do the fish look like they are grasping for air?
(*)what type of fish is this
(*)how large is the tank?
I apologize for all the questions. I feel like this is 20 questions. Lol