Things to watch for
1 A clean body wound may show some blood, but the flesh will be white and smooth with little or no swelling.
2 A clean fin wound will look like a piece of fin missing, with no fin rays showing, no reddening or white edges.
3 When bacteria infect a wound, the flesh will redden, swell slightly and scales may stick up around the wound.
4 Fungus takes on a few forms – usually it’s fluffy and white, like cotton wool, but can sometimes look flat and white. Fungus can be wiped off easily.