Molly care
Poecilia sphenops · Fresh and brackish waters from Mexico to Colombia
Mollies need more room than most livebearers: a 29 gallon or larger tank, warm (72 to 82 °F), hard alkaline water and a group of three or more with more females than males.
- Tank size
- 29 US gal or larger
- Temperature
- 72 to 82 °F (22 to 28 °C)
- Group size
- 3 or more
- Temperament
- Peaceful
- Adult size
- 3.9 in (wild fish, including the tail; fancy mollies are crosses with sailfin mollies)
- pH
- 7.5 to 8.5
- Hardness (GH)
- 12 to 25 dGH
- Lifespan
- 3 to 5 years
- Diet
- Omnivore with a big appetite for algae and vegetables
- Care level
- Easy
In a 29 gallon
30¼ × 12½ × 18¾ in outsideHow to keep mollies
Mollies need more room than most livebearers: a 29 gallon or larger tank, warm (72 to 82 °F), hard alkaline water and a group of three or more with more females than males. They graze algae all day and appreciate vegetable-based food.
Diet: Omnivore with a big appetite for algae and vegetables: flakes with spirulina, pellets, blanched greens. Fish food types compared · how often to feed.
Where they swim: Middle of the tank.
Molly tank mates
Share the temperature and water, and neither side eats, nips or bullies the other. Check the full group in the stocking checker.
Banded gourami
4 in · 30+ gal · 72–82 °F
Paradise fish
3.5 in · 20+ gal · 61–79 °F
Petricola catfish
4.5 in · 30+ gal · 73–79 °F
Bolivian ram
3.2 in · 29+ gal · 72–80 °F
Emerald corydoras
3 in · 29+ gal · 72–82 °F
Celebes rainbowfish
3 in · 29+ gal · 68–82 °F
DrawingRabbit snail
3 in · 20+ gal · 76–84 °F
Convict julie
5.1 in · 30+ gal · 75–80 °F
Keep apart
Pea puffer: Pea puffers belong in a tank of their own.
Convict cichlid: Convict cichlids are aggressive towards peaceful fish such as mollies.
Jewel cichlid: Jewel cichlids are aggressive towards peaceful fish such as mollies.
Demasoni cichlid: Demasoni cichlids are aggressive towards peaceful fish such as mollies.
Red zebra cichlid: Red zebra cichlids are aggressive towards peaceful fish such as mollies.
Auratus cichlid: Auratus cichlids are aggressive towards peaceful fish such as mollies.
What a molly tank needs
A tank of 29 US gallons or more (such as the 29 gallon) with a cover, and the equipment below.
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Aqueon PRO QuietFlow Power Filter 20
Rated by the maker for up to 30 US gal, which covers a 29 gallon molly tank without being built for a far bigger one.
Aqueon QuietFlow Internal Power Filter 15–30 gal
Rated by the maker for 15–30 US gal, which covers a 29 gallon molly tank without being built for a far bigger one.
Cobalt Aquatics Neo-Therm Pro 100W
Mollies need 72 to 82 °F; most homes run cooler, so a heater holds the temperature.
API Freshwater Master Test Kit
Tests ammonia, nitrite, nitrate and pH, the readings that matter most before and after adding mollies.
Seachem Prime 100 mL
Removes chlorine and chloramine from tap water at every water change.
Fluval Edge Thermometer
Shows the water temperature at a glance, so you know it stays within 72 to 82 °F.
More choices, each with the reason it is in or out: Filters for a 29 gallon tank · Heaters for a 29 gallon tank. We don’t list fish food: any good brand of the foods under Diet will do. Plan the whole tank's equipment →
Common molly problems
- Shimmying (rocking in place) usually means soft or acidic water or cold water; test pH and hardness.
- They breed readily; plan for fry.
Test the water first whenever fish look unwell: see what your readings mean, then match the symptom. For disease, a vet who treats fish can diagnose it and advise treatment.
More to compare
Sources
Name, origin and adult size checked against Wikipedia: Poecilia sphenops. Temperature, pH, hardness, group size, lifespan and minimum tank size are common hobby guidance, not figures from that article. Ranges are the range the species tolerates; aim for the middle. Minimum tank sizes are for an adult group. Drawings are our own; photo credits follow.
Photo credits
Real photographs from Wikimedia Commons, resized and cropped to fit; each is used under the license named.
- Molly LPA74, CC BY-SA 4.0, via Wikimedia Commons
- Banded gourami Sandipan Das, CC BY 4.0, via Wikimedia Commons
- Paradise fish André Karwath; edited by Muhammad, CC BY-SA 2.5, via Wikimedia Commons
- Petricola catfish Nerezza, CC BY-SA 3.0, via Wikimedia Commons
- Bolivian ram HenryC88, CC BY-SA 4.0, via Wikimedia Commons
- Emerald corydoras NonstickRon, CC BY-SA 2.0, via Wikimedia Commons
- Celebes rainbowfish Brent Tibbatts, CC BY 3.0, via Wikimedia Commons
- Convict julie Regani, Public domain, via Wikimedia Commons
- Pea puffer Beta Mahatvaraj, CC BY-SA 4.0, via Wikimedia Commons
- Convict cichlid S. Olkowicz, CC BY 2.5, via Wikimedia Commons
- Jewel cichlid NasserHalaweh, CC BY-SA 4.0, via Wikimedia Commons
- Demasoni cichlid lee Nachtigal, CC BY 2.0, via Wikimedia Commons
- Red zebra cichlid Maha Dinesh, CC BY-SA 3.0, via Wikimedia Commons
- Auratus cichlid Vlad Butsky from San Jose, CA, USA, CC BY 2.0, via Wikimedia Commons
- Guppy Marrabbio2, CC BY-SA 3.0, via Wikimedia Commons
- Endler's livebearer Dgrummon, CC BY-SA 4.0, via Wikimedia Commons
- Platy Monika Korzeniec, CC BY-SA 3.0, via Wikimedia Commons
- Swordtail Usien, CC0, via Wikimedia Commons
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