It is quite possible that the black spot is part of the fishes colouration. Goldfish often have many different colours in many different shapes and shades anywhere on their bodies or fins.
The huge puss-spot is probably a tumor, this is found quite commonly in older goldfish.
probably
I am unaware of "Black Spot" being a disease of fish. So I would say no.
Actually, goldfish don't have a specific gender. They are born as females, but as they grow, they turn into males.
No, only black goldfish are black.
It would look like a black spot on your back.
I would name my black goldfish Fin
You can see a black spot in the center area of the bite.
who knows. maybe it's sick.
no
NO! Black Moors are goldfish they should be fed goldfish food.
yes you can but its not good to it will keep coming back oh and one i had a black head for ages it grew a layer of skin on it