How big do golden Rudd's get?

Golden Rudd are a man made coloured version of the common Rudd (Scardinus erythrophthalmus) which is a native fish of the UK. My knowledge of them only comes from catching them on rod and line. To the best of my knowledge they grow to over 3 lbs. This would make them unsuitable for small aquaria. They would be best in a pond situation.