As you can hopefully see my goldfish has developed this spot (looks just like a pimple) just behind his gill.
When I examined him, the white part was knocked off, leaving the red bit, but it was back looking like the picture this morning.
He is eating, moving and behaving normally. No flashing or twitching. I fed some peas last night and he gobbled them up!
The last water change was about a week ago, and I added some more salt last night to see if that helped. I am going to do another water change now. I'm sorry I don't have any levels- I realised a few weeks ago that my testing kit was years out of date so chucked it The tank is on the small side as he has only one eye, so finds it very hard to find food in a big space, but it is well filtered with a Stingray filter and there are regular water changes.
The tank has been set up for several months, I have had the fish for 12 years and there are no other fish in the tank. Nothing new has been introduced, although about 2 months ago I started feeding a variety of foods (water fleas, flakes, 'crisps', pellets), rather than only pellets.
Sorry it's so long! Does anyone know what this might be?
I'm planning a salt bath tonight.