The short answer
Yes — this is a solid, easy pairing. Guppies and mollies are both peaceful livebearers with very similar needs, so they get along well in a community tank. The main thing to plan for is size and waste: mollies grow noticeably bigger than guppies and are messier, so give them a larger, well-filtered tank than guppies alone would need. Get that right and both thrive.
Why they get along
Both species are hardy, sociable livebearers that enjoy hard, slightly alkaline water and temperatures around 24–27°C. Neither is aggressive, and they don’t compete in a way that causes trouble — they’ll happily shoal loosely in the same tank. Because they’re different species, they won’t crossbreed, so you avoid hybrids, though each will breed prolifically within its own kind. Expect fry.
How to set it up
- Use a 75 litre (20 gallon) tank or larger to give mollies room and dilute their waste.
- Aim for hard, alkaline water — both species prefer it, and soft acidic water suits neither.
- Keep a balanced ratio of males to females (roughly one male to two or three females) to reduce the harassment that comes with keen livebearer males.
- Fit strong filtration and keep up water changes; see the filters guide.
- Include some algae and plant matter in the diet — mollies especially graze.
Related reading
Watch your numbers with all those fry — read how many fish you can keep and how do I know if my aquarium is overstocked? Care sheets: guppy and molly. Set up the tank via the aquariums hub.