Molly Care Guide
The Molly (Poecilia sphenops and related species) is a popular tropical freshwater fish in the UK. Known for its peaceful nature, active behaviour, and wide range of colours and fin shapes, it's a favourite for beginner and community aquariums.
In this guide, you'll learn everything you need to know about Molly care, including tank size, water conditions, compatibility, breeding, and typical UK prices - plus how to buy or sell them locally.
Quick facts about Mollies
Mollies are livebearing fish native to Central and South America. Popular varieties include black mollies, dalmatian mollies, balloon mollies, sailfin mollies, and lyretail mollies.
They are hardy, social fish that thrive in stable, slightly alkaline water conditions.
Poecilia sphenops / Poecilia latipinna
5-12 cm depending on variety
Central and South America
75L (20gal)
3-5 years
Peaceful, active
24-28°C
Omnivore (flakes, algae, vegetable matter, frozen foods)
7.0-8.5
£3-£12 per fish
How Many Mollies Should You Keep?
Mollies are social fish and should be kept in groups.
- A minimum group of 5-6 is recommended
- Keep more females than males (ideally 2-3 females per male)
- Larger tanks are better for active varieties such as sailfins
Keeping too many males together can lead to:
- Chasing behaviour
- Stress for females
- Mild territorial disputes
They are most comfortable in active community groups.
Ideal Tank Conditions for Mollies
Providing the right environment helps mollies stay healthy and colourful.
- Tank Setup: Spacious community aquarium with open swimming space
- Substrate: Sand or gravel substrate
- Plants & Decor: Live plants and open areas for swimming
- Water Conditions: Slightly hard, alkaline water preferred
- Filtration & Flow: Moderate filtration with stable water quality
- Lighting: Moderate lighting
Mollies appreciate clean, well-oxygenated water.
Compatibility with Other Fish
Mollies are peaceful and suitable for community aquariums.
- Good Tankmates: platies, guppies, swordtails, corydoras catfish, rainbowfish, and peaceful tetras
- Avoid: aggressive fish and fin-nipping species
Long-finned varieties may be vulnerable to fin-nipping.
Are Mollies Easy to Care For?
Mollies are easy to care for and suitable for beginners.
They require:
- Stable water quality
- Slightly alkaline water
- A varied diet with vegetable matter
- Peaceful tankmates
They are hardy but can be sensitive to poor water conditions.
Molly Price in the UK
In the UK, mollies typically cost between £3-£12 per fish depending on variety.
Prices vary depending on:
- Colour and fin variety
- Size and sex
- Availability
- Shop vs hobbyist sellers
Sailfin and speciality strains may cost more.
Where to Buy Mollies in the UK
Mollies are widely available in UK aquarium shops and from hobbyist breeders.
Sourcing fish locally can:
- Reduce transport stress
- Allow you to assess colour and health
- Offer better value
TankMate UK helps connect fishkeepers who want to buy, sell, or rehome fish safely - without shipping.
Can You Sell Mollies?
Yes - mollies are commonly bred and sold by hobbyists.
Selling locally is often the best option, as it:
- Minimises stress for the fish
- Avoids the risks of shipping
- Connects you with other aquarists
TankMate UK allows you to list fish quickly and find local buyers.
Breeding Mollies
Mollies are livebearers and breed very easily.
Key Tips
- Keep more females than males
- Provide plants or hiding spaces for fry
- Gestation lasts around 4-6 weeks
- Females give birth to live young
Adults may eat fry unless cover is provided.
Common Problems with Mollies
Shimmying behaviour, often caused by:
- Poor water quality
- Incorrect water hardness
- Stress
Fin damage or disease, linked to:
- Poor maintenance
- Aggressive tankmates
Overpopulation, caused by:
- Frequent breeding
Why Mollies Are So Popular
- Wide range of colours and fin shapes
- Peaceful and beginner-friendly
- Easy to breed
- Active and social behaviour
- Excellent community fish
When kept correctly, mollies bring colour, activity, and personality to tropical aquariums.
Frequently Asked Questions
Yes, they are hardy and beginner-friendly.
At least 5-6, with more females than males.
Yes, they are prolific livebearers.
At least 75 litres, with more space preferred for larger varieties.
Looking to Buy or Sell Mollies Locally?
TankMate UK connects fishkeepers who want to buy, sell, or rehome fish safely within their local area.
Whether you're adding colourful livebearers to your aquarium or passing fish on to a new home, you can:
- Browse fish available near you
- List your own fish in minutes
- Avoid the risks of shipping
Explore local listings with TankMate UK and find the right fish for your aquarium.