Theres a pale yellowish dot outlined in red (the size of three periods) in the middle of my fish's dorsal fin

Question

what could it be? shes a goldfish, and she seems happy and not stressed or anything.

could it be like, a scartch or scab ?

Answer 1

Is the dot over one of the rays (like bones) in the fin? It could be the fish had a physical injury by bumping into a filter or ornament in the tank. The size sounds too large of a spot to be ich.

There's a possibility that this could be a larval parasite, so I'd advise keeping an eye on that area for a few days. See the photos of parasites, especially Lernea (anchorworm). If your fish develops this, you can treat her with an antiparasitic medication, or one that contains copper following the directions. But I'd wait to medicate until you know for certain that you have a parasite. You can add a tablespoon of non-iodized salt (rock, kosher, canning, aquarium salt) for every 5 gallons of tank water as well - this will help if it's a parasite, or to help prevent fungal infection at the site.