black to orange

[RABENA]

My gold fish went from pure black to bright orange what does this mean and does it always happen. He looks great eating and swimming well I'm a little confused

 

[Rokuzachi]

I believe that black is the most unstable color for goldfish (I read this somewhere, don't remember where).

My black moor is almost completely bright orange now and he's fine (2+ years old). My fancy went from mostly black to pure orange with a red tint, so I don't think you have to worry.