My pacu got stuck in a rock

Question
I'm 16, and have been keeping fish for a while, I have one 10 gallon, a 60 gallon and a 100 gallon pond that I share with my dad. He is setting up a aquaponic system in the pond, but we have a filter(I don't know what type) in it, and currently have some bamboo in the garden box. We recently bought a pacu for the pond, and he got stuck in a holey rock, we got him out but he is missing a lot of scales and his fins are all torn up, do you have any tips that will help him recover faster? He is 2 1/2 inches big. His pond mates are 7 inch long gold fish, a foot long blue channel catfish, a 5 inch sunfish, and his buddy a kio. We took out the rock once we got him out.)
Thanks,
Gabi

Answer
Gabi,
The best way to treat him is to do a 25% water change now and add aquarium salt to his water. Before any treatment, remove him from his tank and place him in your hospital tank. You do not want to treat any fish if there is nothing wrong with it. I am unsure where the Pacu is housed but the ratio is 1 teaspoon of aquarium salt to 1 gallon of water or 1 tablespoon salt to every 5 gallons of water. Once you have the salt in the water, add some  Methylene Blue. It is an excellent and strong anti-fungal medication. Just follow the directions on the packaging. I would also add some Stress Coat to his water. Make sure his water temperature is between 78 and 80 degrees. Anything lower will make healing him very hard.