I need help ASAP!

[xxaprilrose]

Yesterday I did a very stupid thing and add algae fix to my flowerhorns tank. Within 30 mins he was sitting at the bottom and looked very lethargic so I did a 75% water change. He’s still very lethargic and barely moving and super swollen. He won’t eat. Idk what to do. I’m about to do another 50% water change but should I have salt or melafix? Or is he just too far gone?? I always research EVERYTHING before I buy it but this one time I had no idea. I just wanted the algae gone

 

[Colin_T]

Just do a big water change and gravel clean the substrate every day for a week. Change 75% of the water each day.
Make sure the new water is free of chlorine/ chloramine before it's added to the tank.

Clean the filter too so you get rid of any chemicals in the filter.

Do not add anything else because the fewer chemicals going into the tank, the less damage that occurs to the fish.

Increase aeration/ surface turbulence to maximise the oxygen in the water.

Add some carbon to the filter if you have some. If you don't have any carbon it's not a major issue and just do the big water changes.