This situation with fang is ultra rare but for general infections, such as fin and tail rot, open wounds, shank marks from aggression, and mouth fungus. I have allways used maracyn and maracyn2 together.
The thing with any bacterial infection is unless you can isolate the bacteria. And then find a specific antibiotic to kill that bacteria, Then all you can do is use broad spectrum antibiotics which treat alot of different bacteria.
Thats why i allways keep maracyn1 & 2 on hand. They are a mixture of antibiotics that treat pretty much all known bacterial infections in fish. And they come in easy to use pre-measured packets.
I have ued maracyn 1 and 2 on Tats, scombs, 20 or so cuda and several other fish with no ill effects.
Just be aware that treatment is expensive.(I have spent over a hundred on meds for a 50 dollar Tat before) And you need to treat for at least a week to 10days. And it has to be done in a hospital tank because antibiotic means kills bacteria. And it will kill off your bio filter the same as the bacteria in the eye.
So it may cost you a few hundred to treat a monster army like fang in a monster hospital tank/tub. But that fish deserves it IMO.
Good luck and keep us posted
