Perhaps you mean 'Clamped fin'. Clamped fin is caused either by parasites or poor water quality.
If you mean 'Fantail'. A fantail is a fish with 2 tails instead of one. They are harder to keep than goldfish but are much prettier
By the bottom fin, under the belly. The male's fin looks like a straight line and the female's is fanned out.
I would name my black goldfish Fin
Yes, but normally they grow back slowly. However, if fin rot has reached the base of the fin, then the goldfish would be in pain the rest of its life.
it my not your
yes
yes, but it may kill the goldfish
A goldfish has about 1,500 bones inside of it.
Because there is no hard or tough tissue inside of the fin to keep a erect shape.
Caudal fin
Use a medicine called Mr. Yellow found in medical stores and pet shops. This cures fin rot.
Goldfish have key spots on their body, such as the dorsal fin, caudal fin, and anal fin. These spots contribute to their overall appearance by adding color and pattern to their scales, making them visually appealing.
A goldfish's dorsal fin may be down due to stress, illness, poor water quality, or injury. It is important to monitor your goldfish's behavior and environment to determine the cause and address any issues promptly.