Hi again, Nat. Using a flash for photos is okay. There's a good amount of backlighting in these shots from what looks to be a bright window behind the tank. One tip that often works quite well is to try taking photos in the evening. Darken your room lighting and turn on the tank lights, then try some shots without the flash. If your subject fish is in a hospital tank or basin setup with no light, a bright lamp nearby might help brighten the image (probably with the flash on too). My camera auto-focuses on the glass, so fish deeper inside tend to blurr more than they do if I happen to catch them closer to the front. If you try some new photos, taking a step or two further back might sharpen the focus a little better. We can always use a graphic editor to enlarge a small photo somewhat if the focus and resolution is clear enough.
Some thoughts at this point and, yes, even more questions to ask you:
My first question is how's the moor doing today since you posted yesterday? Any changes for the better or worse? Is the fish eating normally and how else is he behaving? Are there any new spots or bumps forming anywhere? Do you see any overall changes in his slimecoat? Is he having any difficulty breathing? Lastly... is the moor flashing or scraping himself against anything?
The affected area of this open sore or wound site is much larger - now that I can see it - than I was expecting. Could you tell us if you believe it has grown to this size on it's own or do you think the other goldie nipping at him made it bigger? Your observations, whatever they may be, are the best help you can give us.
In your original post, you described this area as a noticeable white spot. Did that appear to be mostly at the surface only or did it seem to emerge through the skin from below? As this became more of an open wound (possibly due to this spreading or aggravation by his tankmate), did you see anything that looked white and stringy coming from the sore? Was the white part more grainy or crusty looking, slimy looking, or cottony?
Unless they're caused by trauma/injury, white or red sores on the body with some fungus-looking growth are generally caused by bacterial infection. Where this becomes more confusing, however, is that bacterial infection is often secondary to flukes or other parasites. So further treatment for those in addition to the sore itself may become necessary. We'll be better able to determine that after hearing how you answer some of these questions.
For now, I would suggest adding 1 teaspoon of salt per gallon to the water as a tonic -- completely
predissolved in some of his water first. This helps reduce stress he might be under right now due to the open sore. The addition of salt to the water will diminish oxygenation, so make sure this tank is getting good aeration. We might ask you to increase the salt concentration or recommend other stronger measures after hearing updates from you again. (If he's doing a lot better already and the wound appears to be healing, of course, this won't be necessary.) Be sure you also keep up with daily water changes the whole time he is quarantined and siphon away any leftover food or debris that you may see.
There are two things I was hoping to see from your photos that I just can't make out at all, so I'll ask about those and attach some other images of sores with white edges for you to use for comparison. Would you describe the sore as looking whitish pink, a medium pink, or more red/dark red? I also can't tell how deep it looks... so here are some photos for you to look at to give us those answers.
