Molly

• ExerciseModerate

  An active swimmer that appreciates open swimming space.

• GroomingEasy tank upkeep

  No grooming here — steady water quality and routine tank care do it.

• Living spaceNano-tank friendly

  Happy in a small, stable, well-filtered tank.

• Owner experienceSome experience helps

  A little know-how makes life smoother.

• Commitment3–5 years

  Plan for a long, loving relationship.

Health to watch: Ich (white spot) · Fin rot · Skin conditions

The molly (Poecilia sphenops and relatives) ranges through the fresh, brackish and even coastal waters of Central America, Mexico and the southern United States. Depending on variety it reaches 6–10 cm and lives 3–5 years. Its tolerance of salinity makes it unusually adaptable among aquarium fish. Mollies do best in groups in a tank of 75 litres or more, at 24–28°C with a hard, alkaline pH of 7.5–8.5. Many keepers add a little aquarium salt, and sailfin varieties especially benefit from mineral-rich water. They graze constantly, so live plants and surfaces coated in algae keep them occupied. As omnivores with a strong herbivorous streak, mollies need plenty of vegetable matter — algae, blanched spinach and spirulina flake — alongside standard fare. They are livebearers that breed freely, so expect fry. The classic molly problem is 'the shimmies,' a stress response to soft or unstable water, along with ich and fin rot; steady, hard, warm water is the cure.

• How active is a Molly?

  Moderate. An active swimmer that appreciates open swimming space.

• How much maintenance does a Molly need?

  Easy tank upkeep. No grooming here — steady water quality and routine tank care do it.

• What tank size does a Molly need?

  Nano-tank friendly. Happy in a small, stable, well-filtered tank.

• Is a Molly a good fit for first-time owners?

  Some experience helps. A little know-how makes life smoother.

• How long do Molly live?

  3–5 years. Plan for a long, loving relationship.

• What health issues affect the Molly?

  Keep an eye out for Ich (white spot), Fin rot, Skin conditions. These are worth raising with your vet, along with any screening they recommend.

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