Goldfish changing color

[Luvlee2660]

I have had my goldfish Dorothy for a little over a year now and in January I upgraded her and my pleco to a tank a little over 30 gallons. I got two other goldfish after that who are a different type but doing fine. For some reason my big goldfish has lost all her orange color? I was hoping someone knew why, I attached a before and after pic of her as well. I have a big penguin filter, bubbler, and filter that takes out harmful ammonia and nitrites (nitrates?). I also change the water every month or sooner. Any thoughts?

 

[SomeRandomGuy]

Goldfish naturally change color as they get older. Though they can lose color when they dont get enough light. If you kept a fish in the dark for a month, it would be all white. Also it depends what food you feed them too.