Not a hair. A strand of slime that looks like it's coming from its #17#####. There seems to be a couple of white lumps in it. I'm wondering if it's eggs, None of the things I have read about goldfish breeding say anything about slime.
The one in the pic is gone now and there is another one developing.
I've replied on your other thread, but it's just poo; fantails and other short bodied goldies do tend to suffer with poor digestion.
Don't feed the fish at all for a couple of days (and I'd recommend you have one 'fast day' every week) and then give some lightly cooked, shelled peas (which it's also a good idea to feed once a week) and that'll help keep it's digestive system in good health.
Long, pale poo can be sign of intestinal parasites, it's true, but if the fish is eating well and is in otherwise good health, I'd just put it down to the weird digestive tract of fancy goldfish!
Thank you for your help. I'm going to take your advice with the fast day. I already give them peas once a week. Apologies for posting in 2 categories but I was anxious to get an answer in case I needed to start a treatment.