What water pH do guppies and mollies both tolerate?

pH 7.2-7.5 works for both species. Mollies can handle this range, and guppies do better here than in the higher pH mollies prefer.

Will guppies and mollies breed with each other?

Guppies and mollies are both livebearers but are different genera. They do not crossbreed, though both will produce offspring frequently within their own species.

Do guppies and mollies have similar dietary needs?

Yes. Both are omnivorous and eat flakes, micro-pellets, brine shrimp, and bloodworms. Feed small amounts 2-3 times daily for best results.

Can Guppy Live With Molly?

By Alex WalshLast reviewed Apr 18, 2026

It depends

Maybe, this pairing works if water is kept on the harder, alkaline side where mollies thrive, though guppies prefer softer water.

Why

Guppies stay at 2 inches and are active, colorful livebearers that do best in slightly soft to neutral water.
Mollies grow to 4-5 inches and are active swimmers that prefer harder, more alkaline water (pH 7.5-8.5 in the wild).
The temp overlap is wide (72-82F) and pH overlap exists at the neutral-alkaline boundary (7.0-7.8).
Both are livebearers and roughly peaceful, so aggression between them is not the concern.
The real issue is water chemistry preference , guppies tolerate harder water, but prolonged exposure to high pH stresses them.

Minimum shared tank

20 gallons

Shared temperature range

72-82°F

What could go wrong

Guppies kept in consistently hard, alkaline water (pH 7.8+) over months may show faded colors, fin deterioration, and reduced immune response.

Gear for a shared tank

Sized for the 20 gallon minimum this pairing needs. Affiliate links — we earn a small commission if you buy through them.

AquaClear 30 Power Filter

Oversized filtration is what lets you stock two species together without water quality crashing. Rated for a tank slightly larger than the 20 gallon minimum.

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Eheim Jager 150W Thermostat Heater

Holds a steady temperature inside the 72-82°F window both species need.

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API Freshwater Master Test Kit

Keep ammonia, nitrite, and nitrate in check. Two-species tanks have more bioload and less margin for error than single-species setups.

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Better pairings to consider

This pairing works if you commit to pH 7.2-7.5 , mollies tolerate it, guppies thrive. If you cannot maintain stable neutral-alkaline water, keep guppies with other small livebearers or soft-water community fish.