I wish I could say what that is, but I'm also pretty new. I saw a website the other day with a lot of goldfish diseases listed - I think it might have been Koko's goldfish. I would suggest quickly calling a reputable fish store near you or you will have another disaster. Take a fish to them to see. Are there "fish doctors" in your area? I think we all need to get some for accurate diagnoses.

Anyway, IMO, quarantine should last until the fish is cured or dead. I know how hard it is to isolate one, but the damage to all can be deadly. Good luck. Let us know how it turns out.

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55 gal. tank-3 Koi, 3 Shubunkin, Black Moor, 2 Goldfish, 1 Calico Telescope, 2 Sarassa Comets, 1 strange Fantail.