They are broadly described as having a body of "golden-green shining color",[8] but a more precise source states that young fish are golden-bronze[9] but darken with maturity,[9] until they gain a dark green back, deep bronze upper flanks, and gold on the lower flanks and belly,[9] and reddish[citation needed] or orange[10] fins,[11] although other colour variations exist. One distinguishing characteristic is a convexly rounded fin, as opposed to goldfish (or C. gibelio) hybrids which have concave fins.[10][12]