A male goldfish can be identified by tiny white pimples popping up on the cheeks and the leading edge of the pectoral fins. But what does it mean when white pimples show up in the cap or wen of a goldfish?
It does not speak to the fish being male. And fish with a decent, heavy wen is vulnerable to this and admittedly, it is unsightly. First, it only happens in fish with head growth, a cap or wen. Orandas are predominant in the fish that have this but lionheads and ranchu are also victims at times.
What you’re seeing is a collection of white blood cells, I’ve looked at the contents of these white pimples under the microscope. And all it is, is a collection of white blood cells and debris. There aren’t even a lot of bacteria in the material. I don’t know if it’s a bacteria, a virus, or just the poor blood supply to the wen or cap tissue which allows these “infections” (almost ‘sterile abscesses’) to occur.
No matter, this does not persist indefinitely, and works itself out if the fish are in warm (ish) water in the mid to high seventies (Fahrenheit) and the water quality is good.
NO treatment is indicated unless the fish also has poor body language (for example clamped fins, shimmying or piping at the surface.)
Doc Johnson