I've had a garden pond for several years. I have a couple of ghost koi, shubunkins and gold fish. Every year for the past few the fish have had babies. As usual all the babies are black or 99% black when tiny but change as they grow. Last year I noticed one that was quiet big that was still black and today I've seen it again. It is now about 5 inches long and totally black but is shaped like a goldfish. Will he change or is this normal for some to stay totally black?