Home / Fishes / Killifish and livebearers / Cyprinodon julimes
No federal permit to keepCyprinodon julimes
Cyprinodon julimes
Fishes › Killifish and livebearers (Cyprinodontiformes) › Cyprinodontidae (Pupfish)
The Julimes pupfish (Cyprinodon julimes) (Spanish: cachorrito de Julimes) is a species of killifish in the family Cyprinodontidae.
Care at a glance
Species-specific aquarium care
- Water: Freshwater.
- Layout: Uses both the bottom and open water: give open swimming space plus cover near the substrate.
- Availability: Rarely or never seen in the aquarium trade; expect to source it from specialists or not at all.
Calculated from this species' own FishBase record: tank size from its typical adult length and swimming zone, water values from its recorded ranges. The group guide below fills in general care.
Care guide
Species care notes
- Tank: a base of at least 24 × 12 in (roughly 14 US gallons); space needed is rated “modest tank”.
- Behaviour: a shoaling fish best kept in a group of six or more; not a community fish.
- Difficulty: Moderate (Seriously Fish rating).
Short excerpts from the species profile:
- Setup: “Need not be too complicated so long as there are plenty of broken lines-of-sight.”
- Diet: “Wild specimens have been observed to feed on diatoms, cyanobacteria and small invertebrates.”
From the Seriously Fish profile for this species, which has the full habitat, maintenance, diet, behaviour and breeding write-up 167
Pupfish
Applies to most species in this group. Habitat: These fish occupy shallow vegetated fresh or saline waters, ranging from Florida marshes to coastal lagoons and the isolated Devils Hole pool. [fg179-flag, fg179-sheep, fg179-fws]. Individual species can differ, so compare with the species numbers above and the linked sources.
Housing & setup
- For a flagfish pair, use at least a 60 × 30 cm footprint; groups need more room.
- Break sightlines with plants or spawning mops to provide cover between territorial males.
- Use sponge filtration when eggs or fry are present.
- Encourage filamentous algae for flagfish grazing.
- Flagfish: pH 6.5–8.5 and 2–20 dGH; establish species and population requirements before choosing fresh or saline conditions.
Climate & lighting
| Water | 64.4–86°F |
Diet
- Algae or an algae-containing prepared food for flagfish.
- Small live or frozen Artemia and Daphnia.
- Small bloodworms and other appropriately sized invertebrate foods.
Social life
- Flagfish males form territories; keep groups only with sufficient cover and space. Species-only maintenance is preferable for breeding.
Health watch
- Aggression injuries under overcrowded conditions; a general aquarium-fish risk.
- Ammonia-associated gill damage in inadequately cycled systems.
- Skin parasites or secondary bacterial infections introduced with new fish.
Understanding the animal
About this animal
About this animal
This pupfish is endemic to El Pandeño, a hot spring in Julimes, Chihuahua, Mexico, and it is adapted to life in water that reaches temperatures as high as 46 °C (114 °F). Consequently, it has been referred to as the "hottest fish in the world", although the closely related Cyprinodon pachycephalus can occur in somewhat warmer waters.
Quoted from the Wikipedia article “Cyprinodon julimes” (CC BY-SA 4.0) 174
In the wild
In the wild
From this species’ own FishBase record (habitat, bottom type, water and breeding data), not its family. Good care copies these conditions.1
| Where it lives | Lives in freshwater. Uses both the bottom and open water. |
| Water it lives in | Freshwater. |
| Climate | Tropical climate. |
From the sources
From the sources
Quoted from the matching sections of reputable sources for this exact species. Specialist databases are used first; Wikipedia (community-edited, CC BY-SA 4.0) only fills gaps. Other sources are short credited quotes.
| Overview | The Julimes pupfish (Cyprinodon julimes) is a species of killifish in the family Cyprinodontidae. This pupfish is endemic to El Pandeño, a hot spring in Julimes, Chihuahua, Mexico, and it is adapted to life in water that reaches temperatures as high as 114 F. Consequently, it has been referred to as the "hottest fish in the world", although the closely related Cyprinodon pachycephalus can occur in somewhat warmer waters. Cyprinodon julimes was scientifically described in 2009 as similar to Cyprinodon eximius, but it has a bigger head, nearly one-third of its standard length. — Wikipedia (community-edited) |
| Where it lives | Home ranges Population dynamics Growth parameters Max. ages / sizes Length-weight rel. Length-frequencies Mass conversion Recruitment Abundance Life cycle Reproduction Maturity Maturity/Gills rel. — FishBase |
| Behavior | Females and young group in small schools. They feed on detritus, perifitum (organic matter that collects on the surface of aquatic plants), and invertebrates — including the microendemic cochliopid Julimes springsnail Tryonia julimensis — and were often seen feeding on floating grass seeds. — Wikipedia (community-edited) |
| Appearance and size | Its body is deep, the dorsal and ventral profile is convex and the lower jaw exceeds the premaxilla. The dorsal fin is placed forward with respect to the pelvic fin. Females and young have reticulate patterns of dark and light silver-brownish bands of varying lengths and thickness over the flanks, as well as a conspicuous black spot or ocellus on the distal edge of the dorsal fin. — Wikipedia (community-edited) |
| Conservation | The species is listed as Endangered (P) in the Mexican Endangered Species NOM-059-SEMARNAT-2010. Since 1998, all water flow from "El Pandeño" has been allocated to 36 farmers grouped in the "San José de Pandos Irrigation Society" (SJPIS). The SJPIS farmers utilize an annual volume of 237,000 m3, or 50 lps, for both agriculture and recreation. — Wikipedia (community-edited) |
Data and studies
The numbers
The numbers
Each bar is what one source reports. Where several sources weigh in, the dashed gold band marks their average.
Minimum tank footprint
Seriously Fish recommends a tank base of at least 24 × 12 in (about 14 US gallons).
Sources for this sheet
- Seriously Fish species profiles Experienced keeper or breederLong-running aquarium reference written and peer-checked by experienced fishkeepers and ichthyologists; each profile covers habitat, tank size, water, diet, behaviour and breeding.
- Seriously Fish: Jordanella floridae Experienced keeper or breederAdded in the 2026 source-checked care-guide review.
- FishBase: Cyprinodon variegatus Peer-reviewed researchAdded in the 2026 source-checked care-guide review.
- US Fish and Wildlife Service: Inside Devils Hole Experienced keeper or breederAdded in the 2026 source-checked care-guide review.
- Merck Veterinary Manual: Disorders and Diseases of Fish Zoo, university or veterinaryAdded in the 2026 source-checked care-guide review.
- FishBase (Froese & Pauly, eds.), version 24.07 Peer-reviewed researchThe global scientific database on fishes, maintained by a consortium of research institutions; every value is referenced.
- Wikipedia (species article) Community referenceFree encyclopedia; useful overviews with their own citations. Intro text is quoted under CC BY-SA 4.0.
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