Fish Active during the day

Amazon Molly

Poecilia formosa

iNaturalist Wikipedia

Meet the Amazon molly, the world’s first-discovered asexual vertebrate. This all-female species uses a unique form of cloning to thrive in the sun-drenched waters of the Texas-Mexico border.

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Quick Identification

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Size

5 to 10 cm (2 to 4 inches) in length; weighs approximately 5 to 15 grams

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Colors

Silvery-gray to olive-green scales with rows of small, dark bronze or black spots along the flanks; fins are usually translucent or faintly mottled

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Key Features

Distinctly upturned, terminal mouth for surface feeding
Compact, stocky body with a rounded tail fin
Absence of bright male coloration or elongated dorsal fins
Visible rows of dark speckles on the sides

When You’ll See Them

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Activity pattern Active during the day

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Peak hours 9 AM - 5 PM

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Season Year-round, with peak visibility during the warmer months of March-October

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Diet Omnivorous surface and mid-water foragers that primarily eat algae, organic detritus, and diatoms, supplemented by small aquatic insects and larvae.

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Habitat Slow-moving freshwater or brackish environments, including streams, warm springs, drainage ditches, and vegetated lagoons.

public Geographic range

Where Does the Amazon Molly Live?

Native to the North American continent, the Amazon molly is primarily found in the warm, subtropical waters of the Rio Grande drainage system. Its core range extends from the southern tip of Texas in the United States down through the coastal plains of northeastern Mexico to the Tuxpan River. While its natural range is relatively narrow, this resilient species has established introduced populations in various warm-water habitats across the American Southwest, particularly in areas with consistent thermal springs.

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2 Countries

150K km² Range

Least Concern Conservation

MX Mexico

Marginal

US United States

Marginal

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iNaturalist / Verified observation data

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Behavior

The Amazon molly is a highly social species that travels in schools, though its social structure is one of the most unusual in the animal kingdom. Because the species consists entirely of females, they do not form traditional mating pairs. Instead, they school alongside closely related species like the sailfin molly or Atlantic molly. They exhibit a behavior called gynogenesis, where they mate with males of these other species to trigger egg development, though the male's DNA is never actually used, resulting in offspring that are genetic clones of the mother.

These fish are active and inquisitive, spending most of their daylight hours swimming in the middle to upper layers of the water column. They are relatively bold and will frequently approach the water's surface to investigate potential food sources. In a backyard pond or stream setting, they are peaceful toward other species and contribute significantly to the ecosystem by keeping algae growth in check and serving as a food source for larger aquatic predators.

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Camera Tips

To capture the Amazon molly on camera, you will need a waterproof action camera or a trail camera with an underwater housing. The best results come from placing the camera in shallow, clear water near the edges of a stream or pond where submerged vegetation is present. Angle the camera horizontally to capture the side profile of the fish, which highlights their characteristic spotting and body shape; top-down shots from above the water are often ruined by glare and surface ripples.

Baiting is an excellent strategy to bring these fish into your camera’s field of view. Use a small mesh feeder bag or a weighted stone smeared with algae paste or crushed fish flakes. Amazon mollies are naturally curious and will quickly swarm a food source, providing excellent group shots. For the best lighting, aim to record during the middle of the day when the sun is directly overhead, as this allows light to penetrate the water and reveal the subtle iridescence of their scales.

Since standard PIR motion sensors often fail to detect movement through water, use a 'time-lapse' setting on your trail camera, taking a photo every 15 to 30 seconds. Alternatively, set an action camera to record short video clips at 60fps, which will allow you to slow down the footage later and see the fast, jerky movements of the mollies as they forage. Ensure your camera is tethered or weighted down, as even slow currents can move a lightweight housing out of position.

Similar Species

Species that look similar or are commonly confused with Amazon Molly.

Sailfin Molly

Males have a massive, sail-like dorsal fin and bright orange or blue highlights, whereas Amazon mollies are all female and more subtly colored.

Atlantic Molly

Virtually identical in appearance, but Atlantic molly populations include both males and females and have slight genetic differences.

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Frequently Asked Questions

Amazon mollies are strictly diurnal, meaning they are most active during daylight hours. They are most visible from mid-morning to late afternoon when the water is warmest and light levels are highest for foraging.

If you have a freshwater pond in their native range, maintain plenty of submerged aquatic plants and rocks where algae can grow. They are also attracted to supplemental feedings of high-quality flake food or algae wafers.

They are primarily herbivores and detritivores, eating large amounts of algae and decaying organic matter. However, they will also opportunistically eat small insects, larvae, and tiny crustaceans found in the water.

Yes, in South Texas and Northern Mexico, they are frequently found in suburban drainage ditches, canals, and garden ponds, provided the water remains warm year-round.

The most definitive way to identify an Amazon molly is the absence of males; if you see a large school of similar-looking fish with no bright, high-finned males, they are likely Amazons. They are also generally stockier than Atlantic mollies but lack the massive dorsal fin found on male Sailfin mollies.

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