In the future..you may want to get a small supply of amoxicilian..500mg capsules...it comes in extremely handy when you get a post-copper or otherwise treated fish with large open wounds from an online dealer...you treat 1 capsule per 10 gallons for about 8-10 days...you have to do daily water changes and replace the cilian after...i have saved a couple of fish this way...works great for preventing secondary infections as well. A great broad spectrum antibiotic....my most recent is a Koran...when I got him from a different online source...he was about 2.5 inches long...had about a half inch gash on his left side...his left fin was just about gone...all looking like either flashing or from extremely rough handling...i FW dipped him to be somewhat safe, put him in the main tank...about 4 days later his left eye became cloudy and looking like it was going to explode from the side of his head...he stopped eating and would barely swim...
I took him out, figuring he was a gonner...I FW dipped him again, set up a quick 10 gallon hosp tank (with bio-balls floating the surface of one of my sumps), a canister filter and 1000mg of amoxicilian to start...10 days later he was fine, the gash started healing up, the fin grew back and they eye cleared up...he is now nearly 5 inches long!