What size tank does a Molly need?

Molly needs a minimum of 20 gallons, with 30 gallons recommended. They are middle swimmers. Keep in groups of 3+.

Is Molly good for beginners?

Molly is rated "beginner" difficulty (1/5). Great for beginners.

What fish are compatible with Molly?

Molly is peaceful. Compatible tank mates include other peaceful fish with similar water parameters (pH 7-8.5, temp 72-82°F).

Molly

Poecilia sphenops

Family: Poeciliidae • Origin: Central America

Mollies are large livebearers available in black, gold, dalmatian, and sailfin varieties. They prefer hard alkaline water and even tolerate brackish.

Min Tank

20 gal

Max Size

4.5"

Temperature

72-82°F

7-8.5

Lifespan

4 years

School Size

Swim Level

middle

Hardness

15-30 dGH

peacefulbeginneromnivoreschooling

Is Molly Right for Your Tank?

Molly is an excellent choice for beginners — rated "beginner" difficulty (1/5). They're hardy, forgiving of minor water parameter fluctuations, and generally easy to feed. A 20-gallon tank minimum is standard — most community setups will accommodate them.

With a peaceful temperament, Molly makes a great community fish. They coexist well with other non-aggressive species of similar size. This is a schooling species — keep at least 3 together, or they may become stressed and display abnormal behavior. Expected lifespan: 4 years with proper care.

Common Mistakes with Molly

✗

Keeping fewer than 3 together

Molly is a schooling species — they need a group of at least 3 to feel secure. Lone or paired individuals become stressed, hide constantly, and may develop health issues or aggression.

✗

Relying on a heater without a thermometer

Molly needs 72–82°F. Heaters malfunction or drift over time — always use a separate thermometer to verify. Temperature swings of even 3–4°F can trigger stress and disease, particularly ich.

✗

Putting them in a tank under 20 gallons

Many beginners underestimate tank size needs. Molly requires at least 20 gallons — ideally 30. Cramped tanks lead to stunted growth, aggression, and poor water quality.