Home / Fishes / Killifish and livebearers / Knife livebearer
No federal permit to keepKnife livebearer
Alfaro cultratus
Fishes › Killifish and livebearers (Cyprinodontiformes) › Poeciliidae (Livebearers)
Alfaro cultratus, the knife livebearer, is a species of tropical freshwater fish from the family Poeciliidae.
Care at a glance
Species-specific aquarium care
- Tank: At least 24 in long and 12 in front to back for one adult (adults commonly reach about 3.0 in / 7.5 cm).
- Water: Freshwater.
- Temperature: 75–79°F (range recorded for this species).
- pH: 6–8.
- Hardness: 5–12 dGH.
- Layout: An open-water swimmer: needs long, open swimming space with few obstacles.
- Diet: A predator: feed meaty foods sized to its mouth (frozen fish, shrimp, worms); it will eat tankmates that fit in its mouth. FishBase classes it as a carnivore.
- 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
- Water: a fairly wide range, from slightly acidic to slightly alkaline, 75–82 °F, pH 6–8, 5–20 dGH.
- Difficulty: Easy (Seriously Fish rating).
Short excerpts from the species profile:
- Setup: “It's most at home in a planted aquarium.”
- Tankmates: “Can be aggressive, especially towards conspecifics.”
- Breeding: “An easily-bred live bearer.”
From the Seriously Fish profile for this species, which has the full habitat, maintenance, diet, behaviour and breeding write-up 167
Livebearers (guppies, mollies, platies and swordtails)
Applies to most species in this group. Habitat: Warm streams, ponds and brackish waters. Individual species can differ, so compare with the species numbers above and the linked sources.
Housing & setup
- Planted tanks with gentle flow; mollies appreciate harder, slightly brackish water.
Diet
- Flake foods with plant matter, plus live or frozen foods.
Social life
- Peaceful community fish; keep more females than males.
Health watch
- They breed constantly; plan for fry or keep single-sex groups.
Understanding the animal
About this animal
About this animal
It hails from Central America and is often kept in home aquaria.
Quoted from the Wikipedia article “Alfaro cultratus” (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, in rivers and streams. Inhabits waters of low to moderate velocity, between 0 and 300 m elevation. Lives on creeks of more than 0.5 m deep, in ditches and near shorelines of large rivers. Generally swims in small groups at a depth of 20 cm. Insectivorous, the young eat mainly aquatic insects and the adults feed specifically on terrestrial insects. |
| Water it lives in | Freshwater, 75–79 °F (24–26 °C), pH 6–8, hardness 5–12 dH. |
| Climate | Tropical climate. |
| Wild diet | Hunting macrofauna (predator). |
| Behavior to plan for | Breeding: internal live bearers. |
What this means for care
- Keep water within its wild range, 75–79 °F.
Native climate (measured)
Native climate (measured)
| Warm-season highs | about 88°F (up to 90°F in the hottest sampled areas) |
| Cool-season lows | about 69°F (down to 67°F in the coldest sampled areas) |
| Average temperature | 77–79°F across sampled records |
| Relative humidity | 83–85% on average (driest month about 82%) |
| Rainfall | about 3530 mm a year, spread fairly evenly |
Measured at 103 wild occurrence records sampled against WorldClim 2.1 climate data (1970–2000 averages). Air conditions in the range are ecological context, not enclosure settings: microhabitats such as burrows, leaf litter or basking rocks can be cooler, warmer or more humid.
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 | Alfaro cultratus, the knife livebearer, is a species of tropical freshwater fish from the family Poeciliidae. It hails from Central America and is often kept in home aquaria. — 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 |
| Reproduction | Gestation lasts for about 24 days. Produces 10 to 30, rarely more, young. Reaches sexual maturity in about 5 or 6 months. — FishBase |
| Appearance and size | It has two knife-shaped rows of scales on the lower edge of its caudal peduncle. Its body is overall olive-gray, paler on the belly, while the flanks have blueish or green hues. The fins are transparent, but the caudal fin develops a dark edging as the fish ages. — Wikipedia (community-edited) |
| Biology | Inhabits waters of low to moderate velocity, between 0 and 300 m elevation. Lives on creeks of more than 0.5 m deep, in ditches and near shorelines of large rivers. Generally swims in small groups at a depth of 20 cm. — FishBase |
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.
Adult length
Maximum recorded length. Measured as total length. Fish in home aquariums often stay smaller than wild records.
Water temperature
Range the species tolerates in nature; aim for the middle.
Sources for this sheet
- 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.
- 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.
- Merck Veterinary Manual: Management of aquarium fish Zoo, university or veterinaryThe Merck Veterinary Manual: a standard veterinary reference written and reviewed by veterinary specialists.
- Merck Veterinary Manual: Types and features of aquatic systems Zoo, university or veterinaryThe Merck Veterinary Manual: a standard veterinary reference written and reviewed by veterinary specialists.
- Merck Veterinary Manual: Nutritional diseases of fish Zoo, university or veterinaryThe Merck Veterinary Manual: a standard veterinary reference written and reviewed by veterinary specialists.
- 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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