Black Molly
Behaviour Peaceful
Typical size 6cm
Max size 8cm
Tank Area Middle, top
Min Tank Size 60cm
Temp Min: 24℃ Max: 28℃
Feeding Flake, frozen, live foods, vegetable matter
pH Range 7.5-8.5
Hardness m,h,vh
Black Molly Poecilia sphenops
  • Black Molly Poecilia sphenops - thumbnail
  • Black Molly Poecilia sphenops - thumbnail

Black Molly

Poecilia sphenops

The Black Molly is a long-standing popular aquarium fish due to its ease of keeping, breeding and tolerance of water conditions. Like many popular aquarium fish however, the species has been over bred to the point that many specimens are weak and require specific conditions in order to remain healthy. Temperature fluctuations, especially cooler temperatures leave the Black Molly prone to disease. A symptom known as 'shimmering' where the fish swims on the spot with fins clamped in an awkward fashion is a common indicator. Skin based problems such as whitespot and velvet disease are also common. The chances of these problems occurring can be dramatically reduced by the addition of aquarium salt to the water. In hard, warm water with added salt the Black Molly is a relatively hardy fish, which is easy to care for, and well suited to a community aquarium. The wild variety is blue/green with orange spots & can tolerate cooler water. Long finned and veil tail varieties are also available, as is a 'balloon molly' variety with a heavily enlarged and rounded belly. It is the opinion of Think Fish that the balloon varieties push selective breeding too far and this variety can only be described as a disabled and deformed fish which has no place in modern, ethical fishkeeping. Males may harass females so more females should be in a group than males. Can be kept in brackish water and even acclimatized to fully saline conditions. Will eat algae.

Family Poeciliidae (Poeciliids) | Other names Molly, Lyretail Molly, Moonfish | Origin Central and South America, Mexico | Breeding Livebearers, females are fertilized internally. Will breed readily in an aquarium | Natural Water Conditions pH 7.5-8.5, medium to very hard | Natural Habitat Freshwater and brackish | Sexing Males are more slender and have an enlarged dorsal fin and pointed anal fin

Have a Black Molly Problem or General Question?

If you have a question about keeping Black Molly's then please use our Black Molly help forum. Join 100's of other fish enthusiasts with 1000's of years experience between them.

question mark     

Think Fish Community Creator - Black Molly

Please check your water type for compatibility with your fish, which can be found on the Black Molly information box.

If you'd like to talk about the "Black Molly" with our users, then we have a buzzing community of fish enthusiasts where you can talk about tank issues, fish behaviour, tank stocking and any other issues related to the Black Molly fish or other types you may have!

To save your details in the Fish Community Creator you must be logged in CLICK HERE to log-in or join

Like this tool? Help keep us online by becoming a think fish supporter and helping with our hosting and development costs!

Tank Details
question mark  Rename your tank:
question mark  Length: (cm)
question mark  Volume: (Litres)
question mark  Filter type:

* This fishtank will only last for this session - to save your tank please Join/Log in

question mark  Max Stocking level: 0cm
0-1 months 20%: 0cm
1-3 months 40%: 0cm
3-6 months 60%: 0cm
question mark  Current stock level: 0cm
Stock percentage: 0%
question mark  Suggested maximum
fish size for your tank:
My Fishtank Quantity Stock cm
There are no fish in your fishtank. To add fish, view a fish profile and click the 'Add to My Fishtank' button
This tool is a guide only. All fish have individual natures and compatibility can never be guaranteed. If you spot anything you think needs improving, contact us at

Click to read the Latest Think Fish Discussions from Thinkfish users.

Tropical Fish Keeping Help and Advice
Fish of the month