Quick Stats
| Adult Size | 8–12 cm |
| Minimum Tank | 20 gal |
| Temperature | 24–28°C |
| pH Range | 7.0–8.5 |
| Hardness (GH) | 10–25 dGH |
| Difficulty | Easy |
| Temperament | Peaceful |
| Diet | Omnivore — flakes, pellets, blanched vegetables, algae |
| Schooling | 3+ (1 male + 2 females) |
Tank Setup
The Black Molly (Poecilia sphenops (black variant)) requires a minimum tank size of 20 gal. For a species this size, a larger tank is always better — more water volume means more stable parameters and a healthier environment.
Water parameters should be maintained within the following ranges: temperature 24–28°C, pH 7.0–8.5, and hardness 10–25 dGH. These are relatively tolerant fish that adapt to a range of conditions.
Provide appropriate hiding places, a suitable substrate, and planted areas to match the natural behaviour of this species.
Tank Mates
Black Molly are peaceful fish. They work well in community tanks with similarly-sized peaceful species.
Compatible tank mates include: Guppy, Platy, Swordtail, Corydoras, Bristlenose Pleco. Avoid housing with aggressive or much larger fish.
Schooling requirements: 3+ (1 male + 2 females). Keeping them in adequate numbers is essential for their wellbeing.
Diet & Feeding
Black Molly are Omnivore. Feed a varied diet to ensure optimal health and colouration.
Omnivore — flakes, pellets, blanched vegetables, algae
Feed small amounts 1–2 times daily. Only provide what the fish can consume within 2–3 minutes to prevent overfeeding and water quality issues.
Common Health Issues
Like all aquarium fish, Black Molly can be susceptible to common diseases including ich (white spot disease), fin rot, and bacterial infections. This species is generally hardy and disease-resistant when kept in good conditions.
Prevention is always better than treatment. Maintain stable water parameters, avoid overfeeding, quarantine new fish before adding them to the main tank, and perform regular water changes. A regular maintenance routine will prevent most health issues.
If disease does occur, isolate affected fish in a quarantine tank and treat appropriately. Always research medication compatibility before use — some treatments are toxic to invertebrates and scaleless fish.
Breeding
Breeding Black Molly is possible in the home aquarium.
Provide appropriate breeding conditions — caves or hiding places for egg-laying species. Condition breeding pairs with high-quality foods before attempting to spawn them.
Many Black Molly will breed readily without intervention. Be prepared to remove eggs or fry if you want to raise them — adult fish may eat their own young.
Frequently Asked Questions
What size tank does a Black Molly need?
A Black Molly needs a minimum tank size of 20 gal. However, larger is always better — more water volume means more stable water parameters and healthier fish.
Are Black Molly easy to keep?
Black Molly are rated as Easy difficulty. Beginners can keep them successfully with proper research and a cycled tank.
What do Black Molly eat?
Black Molly are Omnivore. Feed a varied diet including flakes, pellets, blanched vegetables, algae.
Can Black Molly live with other fish?
Black Molly are peaceful. Compatible tankmates include: Guppy, Platy, Swordtail, Corydoras, Bristlenose Pleco. They work well in community tanks with similarly-sized peaceful fish.