Both kinds of fish look quite similar in appearance to guppies, but as they grow older the k'uhua keeps its slim figure while the ku fish fills out, achieving a height (measured from the dorsal fin to the stomach) 1.5 times that of the k'uhua.
哥兒倆的外形，在幼魚時期頗為相似，而年紀愈長，身材就愈南轅北轍。魚依舊保持細長苗條的身材，高身魚則發展成圓胖型，體高（由背鰭起點量到腹部）是「苦花」的一．五倍；另外，「高身魚」眼睛較小，沒有吻須。