Im sorry to say but not many fish come back from listing upside down.
I don't know what size the tank is but a few gallons probably won't make a huge impact on the nitrate toxicity in the water.
Usually if I suspect a problem I do a large water change like greater than 50% of the tank's volume, making sure that the water is treated with dechloritinator and of the same temp of the tank.
See how he fares until morning and try doing another water change
Sent from my SCH-R950 using MonsterAquariaNetwork App