Hi does anyone have any idea what is wrong with Fats my goldfish. This thing on his nose has come up within the last day or so. He is the only fish in this tank ( soon to be transferred to a new pond ) so he’s not been attacked by another fish .
That may be a bacterial infection but looks more like a possible tumour to me. If it's a tumour you won't be able to treat it, but as long as the fish seems happy and is eating and swimming normally he can live with it. On the chance that it IS just a nasty bacterial infection try an extended course of Esha 2000 and see if that clears it up.