Skip to content
Know your inhabitants. Start with their needs.
aquariumwebshop
Care guide · Freshwater · fish

Montezuma swordtail

Xiphophorus montezumae

Male Montezuma swordtail (Xiphophorus montezumae)
Male Montezuma swordtail. Photo: Loury Cédric, CC BY-SA 4.0. Photo: Loury Cédric (Cedricguppy) · Source · CC BY-SA 4.0Proportionally resized by existing media pipeline; no crop or colour changes.

The Montezuma swordtail (Xiphophorus montezumae) is a livebearing toothcarp from northeastern Mexico. Males are notable for their exceptionally long caudal sword. The fish needs ample swimming room, strong filtration and tankmates that will not nip its fins. Specialist breeder Select Aquatics recommends at least 30 US gallons (about 114 litres); A cautious practical baseline is an aquarium about 80 cm long and around 114 litres; sources differ, and a larger tank gives more room for the striking caudal sword. This guide also covers setup, feeding and reproduction. Aquarium recommendations are not the same as field measurements; body length differs greatly from total length when the sword is included.

Plan your aquarium →

At a glance

Temperature
20–24.5 °C
pH
7.0–8.0
GH
10–20 °dGH
Aquarium length
At least 80 cm
Minimum aquarium volume
At least 114 L
Adult size
Up to 8.5 cm
Group size
At least 3 individuals
Temperament
Territorial

About this species

The accepted name is Xiphophorus montezumae Jordan & Snyder, 1899, in the family Poeciliidae. A male’s total outline including the sword is much longer than its body length; sources use different measurement methods.

Natural habitat

The species occurs in northeastern Mexico, including the Río Pánuco drainage. The Xiphophorus Genetic Stock Center describes flowing rivers and streams over sand, silt, gravel and rock. Keep water clean and well filtered; moderate movement and aeration suit this habitat.

Aquarium and layout

Select Aquatics recommends at least 30 US gallons, about 114 litres; TFH also calls for a large aquarium without giving dimensions. A documented setup with six specimens in an 80 cm tank and a species profile citing about 80 cm support 80 cm as a cautious practical floor, not a scientifically established minimum. Larger is welcome. Plants provide cover. Protect the long sword from fin-nippers.

Water conditions

TFH gives aquarium conditions of 20–24.5°C and pH 7.0–8.0, with medium to very hard water (150–350 ppm). FishBase lists ecological values of 20–26°C, pH 7–8 and dH 10–20. Hardness units are not directly interchangeable; aim for stable, mineral-rich water and adjust gradually.

Behaviour and group size

Males can be intolerant of one another and may spar. TFH recommends plenty of females when keeping a group. Provide space and cover; a species-focused aquarium is a safe choice when you want to reduce aggression or protect the long tail. Avoid boisterous or fin-nipping companions.

Feeding

This species is omnivorous. Offer a complete tropical staple and vary it with suitable small live, frozen or freeze-dried foods. Algae and plant matter should also be part of the varied diet. Algae wafers are supplementary, not a complete staple.

Breeding

Xiphophorus montezumae is livebearing. FishBase describes internal development and reports an approximate four-to-five-week gestation and 15–30 young; these are reference values, not a guarantee for every aquarium. Dense plants provide cover for fry. Plan for repeated broods and decide in advance how to manage offspring.

Sources & review

This care guide draws on several specialist sources and was last checked on .

View the sources