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Shortfin Molly
Poecilia mexicana
Animalia›Chordata›Actinopterygii
📍 Mexico
A wild-type molly species native to Mexico and Central America with a natural, unmodified short-finned body shape and olive-grey to tan coloration with iridescent scales — the ancestor of many popular molly varieties. More streamlined than fancy mollies, it is an active swimmer that adapts well to brackish conditions and is quite hardy.
Care Guide
Diet
Shortfin Mollies are omnivorous and should be fed a varied diet of high-quality flake food, small pellets, and regular supplements of blanched vegetables like spinach and zucchini. Feed small amounts once daily, only what they can consume in 2-3 minutes. They will also graze on algae and plant matter in the tank, which provides beneficial fiber.
Behavior
Active, peaceful swimmers that spend most of their time in mid-water levels, though they will explore all tank zones. They are social fish that do best in groups of 3 or more and exhibit minimal aggression toward tankmates. Males may display mild territorial behavior during breeding season but rarely cause serious conflict.
Breeding
Shortfin Mollies are livebearers that breed readily in captivity with minimal intervention—females can produce 20-60 fry every 4-6 weeks once mature. Provide dense vegetation or breeding box to protect fry from predation by adults. Breeding is easy and occurs frequently in established tanks, making population control important.
Tank Mates
Similar size, peaceful temperament, and identical water parameter requirements make them ideal companions
Fellow livebearers with matching care needs and peaceful behavior; compatible water chemistry
Small, peaceful schooling fish that occupy different water zones and have similar temperature preferences
Peaceful algae eater that won't compete for food and helps control excess vegetation
May be preyed upon by larger mollies; best in heavily planted tanks with plenty of hiding spots
Common Diseases
Fin Rot
Frayed, discolored, or deteriorating fins; lethargy and loss of appetite
Perform 25% water changes every 2-3 days, improve water quality, and treat with antibacterial medication if severe; remove sharp decorations
Ich (Ichthyophthirius)
White spots on body and fins, excessive scratching against objects, rapid breathing
Raise temperature gradually to 28-30°C, increase aeration, and treat with ich medication following label directions; perform daily water changes
Molly Disease (Livebearer Specific)
Curved spine, difficulty swimming, lethargy, loss of appetite, faded coloration
Maintain pristine water conditions with frequent changes, ensure proper diet with vegetable matter, and isolate affected fish; often related to poor water quality or genetics
Constipation
Bloated appearance, reduced appetite, lethargy, stringy feces
Feed blanched vegetables and reduce pellet feeding; offer daphnia or bloodworms as a laxative; ensure varied diet with adequate fiber
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Water it likes
- ph
- 7.0–8.5
- ammonia
- 0 ppm
- nitrate
- <20 ppm
- temperature
- 70–82°F (21–28°C)