Montezuma Swordtail

Looks how to spot one

scales

A slender, livebearing fish with a greenish base colour and iridescent horizontal green stripes, often with spots, blotches or lines. The male has a spectacular 'sword', an elongated lower tail fin edged in black and yellow, that can be twice the length of his body. His dorsal fin is large and sail-like. A pale 'ivory' colour form with extra dark splotching also exists in the hobby.13

Personality what they are like

Shy and peaceful but active. Males are competitive with each other, performing boisterous, acrobatic displays. They can be skittish at first but settle down once a routine is established. They are not aggressive toward other species but their swords may be nipped by fin-nipping tankmates.41

Daily activity how busy a day looks

Moderate activity. Needs a tank of at least 30 gallons (113 litres) with plenty of open swimming space and hiding spots among plants. Moderate to strong aeration and some water movement are beneficial.54

Grooming and care the hands-on bits

Weekly water changes of 50% (or two 25% changes per week) are recommended. Use a filter that removes debris rather than sponge or undergravel filters. Keep the tank clean to avoid mulm buildup, which can cause losses in young fish.6

Home where they are happiest

Temperature 20-26°C (68-78°F), pH 7.0-8.0, hardness 150-350 ppm (moderately hard to very hard). Provide a planted tank with fine-leaved floating plants like Java moss for cover. A bare bottom with a thin layer of pea gravel over part of the tank works well. Keep them in a species-only tank or with peaceful fish that won't nip fins.145

Food basics what goes in the bowl

Omnivorous. Accepts high-quality dry foods, but thrives with live or frozen foods such as baby brine shrimp, daphnia, bloodworms, blackworms and chopped redworms. Also benefits from algae for grazing. Feed 1-3 times daily.416

Company who they like around

Best kept in a group with one male and two or three females to reduce male competition. They are not big fry-eaters, but fry should be raised separately for best survival. Do not house with other Xiphophorus species to prevent hybridisation.41

The story where it all began

Described by Jordan & Snyder in 1899, the Montezuma swordtail is native to northeastern Mexico. It is considered the 'king of swordtails' by enthusiasts, prized for its wild nature and the male's spectacular, horizontal sword, a feature that female swordtails find attractive in sexual selection. Unlike many domesticated swordtails, this species has retained its shy, wild behaviour and subtle iridescent beauty. It has rarely been bred commercially due to its slower reproduction and longer maturation time, but it is well established among specialist aquarists and occasionally appears at auctions, sometimes fetching up to $100 a pair.512

Recognised by the official bits

U.S. Fish & Wildlife Service

Listed as Moctezuma Swordtail (Xiphophorus montezumae)7

ITIS

Accepted species in family Poeciliidae8