Black Swordtail Swordtail
Xiphophorus hellerii
About this strain
A striking, dark strain where heavy melanophore expression covers most of the body in deep black or charcoal, often with a subtle iridescent sheen under light. Males carry a black-edged sword that blends dramatically into the body. The best specimens are nearly uniform black with minimal mottling or pale patches on the flanks. Be aware that pure black swordtails can be prone to melanoma — a real concern with highly melanistic lines — so source from reputable breeders who cull aggressively. Pairs beautifully with high-contrast tankmates in a well-lit aquascape.
Origin
Developed primarily through hybridization with Xiphophorus maculatus (platy) to introduce the 'nigra' melanophore gene, refined by German and American breeders through the mid-20th century. Melanoma susceptibility has been studied scientifically in these lines.