Poeciliidae

Alfaro cultratus

Alfaro cultratus, also known as the knife-edged livebearer, belongs to the family Poeciliidae. This fish is distinguished by its hardiness and unpretentiousness, which means it does not have special requirements for keeping conditions. Although it is not often found in retail chains, this species is quite common among amateur aquarists.

Tank
from 50 L (13 gal)
Temperature
24 – 28 °C (75 – 82 °F)
Size in aquarium
7 cm (2.8 in)
Acidity
pH 6–8
Natural rangeRange on the map
  • Central America area
  • Costa Rica
  • Nicaragua
  • Panama

Tank conditions

Plan the tank stocking
Temperature
24 – 28 °C (75 – 82 °F)
Water pH
Slightly acidic (6) – Slightly alkaline (8)
Water dH
Soft (5) – Very hard (20)
Water salinity
no salt (freshwater)
Size in aquarium
7 cm (2.8 in)
Lifespan
5 years
Temperament
Territorial often aggressive
Toward small fish
not a predator
Required aquarium volume
from 50 L (13 gal)
Lighting
moderate (regular)
Substrate
any (no restrictions)
Water flow
weak or moderate
Swimming level
near the surface
Feeding
Any (universal)
Keeping
Schooling usually from 5–6 individuals and more
Jumping
high a tight-fitting lid is essential
  • Lifespan. A lifespan to expect under good care, not a measured value: it depends heavily on tank volume, water quality and diet — and for selectively bred forms, on their origin as well.
  • Toward small fish. Based on the Predators category in the catalog or the temperament in the species parameters. “A risk to small fish” means the species is not a predator by habit, yet will swallow any fish that fits in its mouth.
  • Required aquarium volume. This is a husbandry recommendation, not a measured value: the volume depends on the keeping mode (schooling (usually from 5–6 individuals and more)), footprint, decor and tank mates.

Care and keeping

Description

The appearance of this fish is quite simple: its coloration is light gray. From certain angles, a bluish tint can sometimes be noticed. The fins remain translucent. The body is slightly elongated, with males usually being more slender than females, who, in turn, are noticeably larger.

Habitat

This species is widespread in the waters of Central America, including the territories of Costa Rica, Nicaragua, and Panama. It prefers to inhabit small rivers, streams, canals, and backwaters where the current is moderate or slow.

Behavior and Compatibility

The fish sometimes shows aggression towards individuals of its own species, but serious injuries are extremely rare. It is compatible with other species if they are larger than it. It is not recommended to keep small fish with Alfaro cultratus.

Care and Maintenance

Alfaro cultratus adapts well to a wide range of pH and GH values, which significantly simplifies water preparation for the aquarium. It is usually sufficient to use tap water that has been left to stand for about a day. The minimum equipment set includes a filter, aerator, heater, and lighting system. Weekly maintenance involves replacing 15–20% of the water volume with fresh water. Substrate cleaning is performed as it becomes silted. In terms of decor, it is recommended to create areas with lush vegetation and open spaces for swimming. Floating plants are also welcome. Roots, snags, and rock formations can be used as additional decor.

Diet

The diet can include any dry, frozen, or live foods. For home keeping, the optimal solution is to alternate several types of food from trusted manufacturers throughout the day. Feeding is recommended 2-3 times a day, offering an amount that the fish can eat in 5 minutes. It is important to promptly remove any uneaten leftovers.

Breeding and Reproduction

Breeding Alfaro cultratus in a home aquarium is not a difficult task. No special conditions for spawning are required, as it can occur in the community tank at any time of year. An adult female can produce up to 100 fry. Upon finding them in the aquarium, it is advisable to transfer the young to a separate tank, for example, a three-liter jar, and feed them micro-food.

Diseases

In a well-balanced aquarium ecosystem, disease outbreaks are extremely rare. Health problems arise in neglected cases when there are high levels of pollutants, irregular or poor-quality feeding, or contact with already sick fish.

How to choose

When choosing Alfaro cultratus, attention should be paid to the overall activity of the individuals in the aquarium: healthy fish should swim quickly, show curiosity, and not exhibit signs of timidity or apathy. It is important to carefully inspect the body for the absence of injuries, ulcers, white spots, or signs of fungal infections, as the species is sensitive to water quality and bacterial infections. Avoid buying fish that stay at the bottom or look emaciated, as this may indicate health problems or stress from improper keeping conditions in the store. Since these fish are active swimmers, it is recommended to purchase a group of several individuals to reduce their stress during transportation and adaptation.

Compatibility

There are no pair reviews for this species yet — check tankmates in the matcher.

All tankmates

Plants and this fish

Matching water does not mean the plant will stay intact.

Frequently asked questions

The essentials: size, tank volume, water parameters and care

How big does Alfaro cultratus get?

An adult reaches 7 cm in length. Plan the tank around the maximum size: the fish quickly outgrows a cramped setup.

What size aquarium does Alfaro cultratus need?

The recommended volume is 50 L. A smaller tank speeds up nitrate build-up and raises stress levels.

What water parameters does Alfaro cultratus need?

Temperature 24–28 °C, pH 6–8, hardness 5–20 dGH. Stability matters more than exact values: sudden swings are harder on the fish than a small deviation from the ideal.

How long does Alfaro cultratus live?

Around 5 years when kept properly. Lifespan depends directly on tank volume, water quality and a varied diet.

Is Alfaro cultratus aggressive?

Temperament: territorial (often aggressive). Keep this in mind when choosing tank mates.

How many Alfaro cultratus should be kept together?

Recommended setup: schooling (usually from 5–6 individuals and more). Ignoring this is a common cause of stress and disease.

What does Alfaro cultratus eat?

Diet type: any (universal). Feed small portions that are finished within a couple of minutes — overfeeding does more harm than underfeeding.

What is the scientific name of Alfaro cultratus?

The scientific name of the species is Alfaro cultratus, family Poeciliidae. It also appears in the literature as: Alfaro acutiventralis, Alfaro amazonum, Petalosoma amazonum.

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Other scientific names and conservation status

Other scientific names
Alfaro acutiventralis, Alfaro amazonum, Petalosoma amazonum, Petalosoma cultratum, Petalurichthys amazonum, Petalurichthys cultratus
Categories
Livebearers
Conservation status
Least concernLC