honestly mate i know it's hard but the best thing to do is treat with melafix, turn the lights off and leave him be for like a week. have plenty of air bubbles in your tank to.
Just an FYI: that is EXACTLY what my 10" common pleco looked liked when he spent the night out of the tank.
In a few days, a lot of his scales will fall off and he'll turn a little white. I did a couple water changes, 25%, and added salt & Amquel+ every other day for about the first week.
It's now been over two weeks and my pleco is almost completely healed!
Also, your little guy has healthy looking eyes (They aren't cloudy) and seems like he's a fighter. Be optimistic, and throw a few weighted pieces of zucchini in there to nibble on.
Don't give up hope. I had a big Oscar jump out. He had to have been out of the tank at least an hour. I found him 15 feet away from the tank with my cat staring at him. He turned out fine. You're doing all the right things. Good luck, I hope it works out.
That poor Dovii is all jacked up. I've found fish dead on the floor a few times and never any ants eating it. No offense intended but it sounds like you have an ant problem you need to get handled.
He needs a hospital tank so he can be alone and stress free. Keep the temp at about 82F and make sure there's plenty of aeration. Add 1tbs of salt per 5 gallons and do daily partial water changes (replacing the salt removed), while trying not to disturb him too much. He should be better pretty soon. Sorry to hear about the fish.