I have a 100 litre aquarium containing one gold fish (bought before I learnt from mn that they should not be kept indoors in small tanks) and half a dozen white cloud minnows. The gold fish is about two years old and about 3- 4 inches long. I have just noticed that it no longer has its orange patches, which, now I come to think of it, have been gradually fading. Why might this be?
A lot of goldfish fade over time, it's normally down to breeding- black is the most unstable colour, then red/orange, and they both tend to fade as goldfish get older. As long as the water quality is good and the goldfish is otherwise healthy then I wouldn't worry too much.
100 litres isn't that small but if you want to keep him healthy then he'll need an upgrade soon. Is he a common goldfish (fish shaped) or a fancy one (fat, round ones, usually with long fins)? It's OK to keep goldfish indoors if they are given the right conditions- in fact, fancy ones need to be kept indoors because they can't cope with predators or cold temperatures.
Glad to hear it, EauRouge. I was hoping that it wasn't a sign of stress. There wouldn't be an option of moving up ... would it be fair or unfair to release it one day in the huge ornamental goldfish ponds at my husband's place of work? It would be tiny in comparison to some fish there ... would it just end up being dinner? It is a normal fish-shaped fish bought for £1 from an aquarium shop before I knew better.