Hi-Fin Swordtail Swordtail
Xiphophorus hellerii
About this strain
The hi-fin (or Simpson hi-fin) mutation produces a dramatically enlarged dorsal fin — often nearly as tall as the body is deep — that flows and waves with every movement of the fish. It can be combined with any body-color strain and is genuinely eye-catching in a calm, well-planted tank. The oversized dorsal is a recessive trait and fish are fully robust when kept in appropriate conditions, but the fin is physically vulnerable: keep water pristine, avoid fin nippers, and ensure gentle flow so the fin doesn't get shredded on equipment. Males are slightly less active swimmers than standard-fin siblings.
Origin
The hi-fin mutation was identified and selectively bred in the mid-20th century, attributed in part to American hobbyist and breeder work. It has since spread globally through commercial aquaculture and remains a popular specialty strain.