My goldfish =[ .?

my goldfish has a big brown/black patch on its head above its eyes and it doesnt look normal what is the black point how did it get it and how can i fix it

plzzzzz help =[
Answers:    Usually any black patches are the sign of medicinal from ammonia burns, but usually this is on the fins, face or stomach. Have you tested your water and how long have your tank been up and running?

You need to oral exam the water.

Also, fungus called Saprolegnia. This is usually due to your fish suffering from some other disease.

Look at your fish guardedly. If the black mark is smooth and seems to be part of his color, itis an ammonia burn recuperative. Clean water with routine partial water change he will heal up. If it looks fuzzy or slightly raised, it is a fungus and needs to be treated near meth blue or another broad spectrium antifungual.
Can glofish be surrounded by equal cistern as fantail guppies?   Discus beside fin rot?   Helppp! Is my fish dying?   Alright adjectives you Betta experts...?