My Black Moor goldfish is turning golden
I have had 3 goldfish, all 3" long counting their tails, in a 10-gallon aquarium along with a mini-algae eater for the past year. Everyone has been doing fine until the past 2 months, when I noticed my Black Moor was losing his black color along the belly. Not losing his scales, but the scales are changing color to gold. Currently his body is now mostly golden, with only black remaining along his upper half of the body, the fins and the eyes. The other two goldfish are a calico and a golden fantail, and neither one of these has shown any changes on their bodies. The mini algae eater is also doing well. Their food intake hasn't changed, and the water pH and nitrate levels are all normal. No one looks sick. Anyone know what's going on with my fish? Thanks.