My red capped oranda has some black stuff on tail and fins. It started with a couple of sliver like black marks on her back fin and 1 on her tail. Now she has more all over her tail and fins. It seems to scrape off with my finger nail, but I don't want to hurt her. The look like black slivers - long and narrow and only on her fins.

Does anyone know what this might me or what I should do?

She lives in my pond and was stuck in a rock for 3 weeks at which time I thought something came and ate her, however, I have never seen any preditors. Then, one day when we drained some water from the pond to clean the filter, she came swimming out sideways and upside down because it seemed she forgot how to swim. Now she has those black things on her. She does not seem sick but I'm afraid something may be eating her fins?

I don't want her to die because she is my prettiest fish. None of the other fish have this.