Simpson Hi-Fin Swordtail Male

The Simpson Hi-Fin Swordtail carries the Simpson hi-fin mutation, which causes the dorsal fin to grow to an extraordinary height — sometimes equalling the body depth — creating a dramatic sail-like profile. Combined with the classic swordtail lower sword and vivid body colouration, this is one of the most impressive swordtail varieties available.

The Simpson mutation is named after the American aquarist who first developed it, and it has been combined with virtually every swordtail colour strain. In hi-fin form, the fish require slightly more horizontal swimming space so the tall dorsal is not damaged against tank furniture.

A moderately demanding variety due to the care required to maintain fin integrity, but immensely rewarding for hobbyists who invest in proper conditions.

Water: 20–27 °C, pH 7.0–8.0, GH 10–20; stable conditions important for fin health. Tank: 100 L minimum; open swimming space; avoid sharp or abrasive decor near dorsal fin. Feeding: High-quality flake, frozen Artemia, colour-enhancing foods; 2–3 meals daily. Breeding: Livebearer; hi-fin is dominant; fry grow to full fin height by 4–6 months. Compatibility: Peaceful; keep with calm tank mates that will not nip the tall dorsal.