If he/she doesn't have a bigger container, in order to save the fish, this is better than nothing, it sounds like a bacterial infection ... This is how I saved my fish, I had him in a 3 gallon for a bit, and changed 95% of the water daily and medicated everyday after water change, fed him prior to water changes.. He survived and is now healthy.... I would do the same thing again in a heart beat.....
Yes an airstone, is necessary, but with the water changes it will be fine, for a short period of time.