Originally Posted by boet
I did a large water change today and maintenance on the filters so hoping that helps.
Changing water and the filter probably won't make any difference. The bacteria are already honed in.
Ideally, if a healthy fish is nicked, a small wound would heal without developing a sore. A sore means that bacteria have gotten a foothold.
I think that you would need to add antibiotics to the tank OR treat the fish with salt, which is highly effective against external bacterial infections. Noga's book on fish diseases recommends a 30 min bath in water with 10-30 grams salt per liter. Monitor fish behavior during treatment and remove fish if it gets too stressed. Then, repeat the salt treatment the next day.