Not furry, but we like them anyway.
Yucatan Molly
Poecilia velifera
Also called Giant Sailfin Molly, Yucatán Sailfin Molly
From Yucatán Peninsula, Mexico1
A friendly guide, not veterinary advice. For anything about your pet's health, ask your vet.
At a glance the quick version
Males typically under 10 cm but can reach 15 cm; females similar or slightly larger.
Looks how to spot one
scales
The body is elongated and laterally compressed, with a large, sail-like dorsal fin in males that can be held erect during displays. The snout and mouth turn upward.4
Personality what they are like
Peaceful and active, well behaved with other species and their own kind. Males may spar by flaring their dorsal fins, but aggression is minimal.31
Daily activity how busy a day looks
Moderate to high. They need open swimming space to develop their sailfin and plenty of room to explore. Strong water movement and aeration are beneficial.3
Grooming and care the hands-on bits
Regular water changes are essential. They are more sensitive than common mollies and require stable, hard, alkaline water. Salt is not necessary but can help during acclimation or illness.36
Home where they are happiest
A tank of at least 40 gallons (151 litres) for a small group, with a pH of 7.0-8.5 and moderately hard to hard water. Provide plenty of plants, open swimming areas, and a covered tank as they may jump. Floating plants offer refuge for fry.34
Food basics what goes in the bowl
Omnivorous with a strong preference for vegetable matter. Feed a diet of algae, blanched spinach, cucumber, vegetable flakes, and supplement with live or frozen foods such as worms, crustaceans, and insects.63
Company who they like around
A peaceful community fish best kept in a group with one male and several females to avoid harassment. Suitable tankmates include other livebearers, gouramis, peaceful cichlids, and Corydoras. They are not known to be venomous or illegal to keep, but check local regulations as they are introduced in some regions.41
The story where it all began
The Yucatan Molly was first described scientifically in 1914 by Charles Tate Regan, based on specimens imported from Progreso, Mexico, to Germany by aquarist Johann Paul Arnold. It was initially mistaken for the related Sailfin Molly (Poecilia latipinna). Its striking colours and large dorsal fin quickly made it popular in the aquarium hobby, and it has been selectively bred to produce fancy varieties. The species is considered vulnerable in its native range due to habitat loss, but it has been introduced to other continents through the ornamental fish trade and mosquito control efforts.1
The care rhythm Furry Diary remembers it for you
A typical home-care rhythm for a Yucatan Molly. It is our own starting plan, not a vet's advice, and you can change every line in the app.
- FeedingSmall amounts once or twice a dayevery day
- Temperature checkevery day
- Water changeAbout 25% of the waterevery week
- Water testevery week
- Glass cleanevery week
- Filter rinseRinse in old tank water, never tap waterevery month
Owner questions the things everyone asks
How often should I feed my Yucatan Molly?
Feed your Yucatan Molly small amounts once or twice a day. Furry Diary's starting plan is to feed daily, but always check the food label and ask your vet for exact portions.63 Furry Diary plan
What does a Yucatan Molly eat, and what should it never eat?
They are omnivores with a strong preference for vegetable matter, so offer algae, blanched spinach, cucumber, and vegetable flakes, plus live or frozen worms and crustaceans. Never feed them anything not listed here; ask your vet for a safe list.63
How much space does a Yucatan Molly need?
A tank of at least 40 gallons (151 litres) is needed for a small group. They need open swimming space to develop their sailfin and plenty of room to explore.34
What temperature, light or water does a Yucatan Molly need?
They need stable, hard, alkaline water with a pH of 7.0-8.5 and moderately hard to hard water. Strong water movement and aeration are beneficial, and a covered tank is important as they may jump.34
How often should I clean a Yucatan Molly's home?
Furry Diary's starting plan is to do a 25% water change weekly, test the water weekly, and clean the glass weekly. Rinse the filter monthly in old tank water, never tap water. Furry Diary plan
Can a Yucatan Molly live with others?
Yes, they are peaceful community fish best kept in a group with one male and several females. Suitable tankmates include other livebearers, gouramis, peaceful cichlids, and Corydoras.41
How long does a Yucatan Molly live?
Lifespan varies and is not specified in the provided information. Ask a good breeder or an exotic-pet vet for typical longevity.
Can I handle a Yucatan Molly?
Handling is not recommended as they are delicate fish with scales. They are not known to be venomous, but avoid touching them to prevent stress or injury.4
Written from the sources on this page, a few checked guides (VCA, ASPCA, RSPCA) and Furry Diary's own starting care plan. A friendly guide, not a vet's advice.
Like what we are building? Buy Archy a bone.
All of this is free for everyone, with a source on every fact, and it will never show annoying ads. It was a big job to build, so if it helped you, buy Archy a bone. Any amount is lovely, and no is a perfectly fine answer too.
Archy is our Australian Cattle Dog and chief taste tester. Tips go to 4V3D OÜ, the small family studio behind Furry Diary.
Where this comes from
Every breed page shows where each fact comes from. If we got something wrong, sorry, we are pet people, not a science magazine. Tell us at [email protected] and we will fix it.
- en.wikipedia.org: Poecilia velifera en.wikipedia.orgused for origin, length cm, colours, temperament, social needs, history, fun fact
- fishbase.se: 4773 fishbase.seused for length cm
- nanfa.org: yucatan sailfin molly poecilia velifera nanfa.orgused for best traits, temperament, activity needs, grooming or care, habitat needs, diet basics, fun fact
- tropicalfreshwaterfish.com: Poecilia velifera tropicalfreshwaterfish.comused for coat or body, habitat needs, social needs
- biogeodb.stri.si.edu: 3294 biogeodb.stri.si.eduused for colours
- seriouslyfish.com: poecilia velifera seriouslyfish.comused for grooming or care, diet basics
- britannica.com: Poecilia velifera britannica.com
- VCA Animal Hospitals: Feeding times and frequency for your dog vcahospitals.comused for owner questions
- ASPCA: Dog grooming tips aspca.orgused for owner questions
- ASPCA: Cat grooming tips aspca.orgused for owner questions
- ASPCA: People foods to avoid feeding your pets aspca.orgused for owner questions
- RSPCA: What to feed your rabbit rspca.org.ukused for owner questions
Checked 2026-10-01. Text is written in our own words from these sources.