rm
Passport
- Family
- Mollies
- Grows to
- 8 cm (3.1")
- Lives
- 3–5 years
- Temperament
- Peaceful
- Care
- Beginner
- Swims
- Mid-water
- Keep
- In a group of 3 or more
- Water
- 21–28 °C (70–82 °F)
VenezuelaColombiaMexico
Care requirements
i
On record for Molly: adult size, lifespan, minimum tank, temperature, ph, hardness, minimum group, diet, care level, swim level, tank length.
A figure that is not on record is left out rather than guessed. One marked Suggested comes from keeping knowledge rather than a page.
- Minimum tank 76 L / 20.0 US gal
- pH 7–8.5
- Hardness 15–30 dGH
- Diet omnivore
- Tank length 90 cm minimum
Care notes written from general aquarium knowledge, not from the cited sources.
About
Mollies are the livebearer with a hardness problem. They're sold alongside guppies and platies as an easy beginner fish, and in soft water they are not easy at all — they develop shimmies, fungal patches and a slow decline that gets blamed on everything except the water.
In hard, mineral-rich water they're superb: big, robust, endlessly active, and available in blacks, silvers, dalmatians, lyretails and sailfins. A mature sailfin male raising his dorsal is a genuinely impressive fish.
Many wild populations live in brackish and even coastal water, and adding a little marine salt is a long-standing trick for mollies that aren't thriving. It works, though hard fresh water usually does the job on its own.
Tank setup
Give your mollies hard, alkaline, mineral-rich water and treat it as the requirement it is. If your tap water is soft, buffer it — crushed coral in the filter is the easy approach.
Give them space. Mollies are considerably bigger than the other common livebearers and a group needs a real tank rather than a starter one.
Plant reasonably and leave open swimming room. They're active and cover ground.
Keep more females than males. Males pursue relentlessly and a lone female is worn down.
Keep the water warm and stable. They're less tolerant of cool water than platies.
Feeding
Mollies are grazers first. In the wild they spend the day rasping algae and biofilm off surfaces, and their gut is built for it.
Feed vegetable food as the base: spirulina flake, algae wafers, blanched courgette, spinach and peas. This is not optional garnish — a molly on a protein diet develops digestive problems.
Add some protein for condition, but keep it secondary.
Avoid: a protein-heavy diet, which is the second most common way mollies are ruined after soft water.
Filtration and flow
Filter well. They're large, they eat a lot of plant matter and they produce real waste.
Give them moderate flow and good oxygenation. They're strong swimmers.
Keep the hardness up and change water regularly. Those two things together prevent most molly problems.
With plants
Mollies graze algae off plants without damaging healthy leaves, and they're genuinely useful for it.
They will eat soft plants if underfed on greens. Feed them properly and the aquascape is usually safe.
Tough species that tolerate hard water — vallisneria, java fern, anubias — suit both the fish and the conditions.
Health
The shimmies are the classic molly ailment: a fish rocking side to side on the spot, going nowhere. It's a symptom of soft water, low temperature or poor conditions rather than a disease, and correcting the water usually corrects the fish.
Fungal and bacterial patches follow the same causes. Reach for hardness and cleanliness before medication.
They're prone to ich after a chill, like most livebearers.
Breeding
Mollies are livebearers and they breed readily, though rather less explosively than guppies or platies.
Females store sperm and produce successive broods from one mating. Fry arrive fully formed and large enough to take crushed flake straight away.
The adults hunt fry with real enthusiasm, so dense planting or a separate rearing tank is what determines survival. Broods are large, and a molly colony grows quickly if you let it.
Tank mates
Avoid8
- Least Killifish Molly grows to 8 cm against Least Killifish at 2 cm, big enough to eat it.
- Scarlet Badis Molly grows to 8 cm against Scarlet Badis at 2 cm, big enough to eat it.
- Common Goldfish Common Goldfish is not safe with Molly: common goldfish and mollies are a bad pairing.
- Demasoni Cichlid Demasoni Cichlid is not safe with Molly: african cichlids and mollies are a bad pairing.
- Electric Yellow Lab Molly and Electric Yellow Lab do not mix: african cichlids and mollies are a bad pairing.
Only with care11
- Convict Cichlid Convict Cichlid is noticeably larger than Molly and may bully it or outcompete it at feeding time.
- Jewel Cichlid Jewel Cichlid is noticeably larger than Molly and may bully it or outcompete it at feeding time.
- Chinese Algae Eater Chinese Algae Eater is aggressive and Molly is peaceful.
- Agassiz's Dwarf Cichlid Molly and Agassiz's Dwarf Cichlid are an uneasy mix: mollies and sth american cichlids - dwarf are a pairing to watch.
- Bolivian Ram Molly and Bolivian Ram are an uneasy mix: mollies and sth american cichlids - dwarf are a pairing to watch.
No conflict is recorded with the other 87 species in the database, so nothing to flag. 2 species are not covered at all, so they could not be judged either way.