Can Molly live with Guppy?

Temperature. Molly does best at 21–28 °C (70–82 °F) and Guppy at 18–28 °C (64–82 °F). They share 21–28 °C.

Water. Their pH ranges overlap at 7–8.

Temperament and size. Molly is peaceful and grows to 8 cm; Guppy is peaceful and grows to 6 cm. Molly swims at the mid and Guppy at the top, which spreads them out.

Tank size and groups. Plan on at least 30 US gallons, the larger of the two cautious minimums. Keep Molly in a group of 3+. Keep Guppy in a group of 3+. A starter mix of 3 Molly and 3 Guppy in 30 gallons uses about 47% of the tank’s bioload capacity under our rules and grades A.

Keeping them together

• Feeding: both feed in open water. Feed small amounts two or three times a day so the slower eater gets its share.
• Aquascape: both are calmer with cover. Plants and floating cover make shy fish come out more, not less.
• Group size: a full group is not optional. A schooling fish kept in too small a group is stressed and more likely to nip or hide.
• Shrimp and snails: neither is a known invertebrate eater, but baby shrimp can still be eaten. Dense moss helps.
• Adding them: add the calmer species first and let it settle for a week or two before adding the other, and only once your tank has cycled.

Open this pair in the checker Add your other fish to grade the whole tank.

Quick facts

Data from the Species Ledger, checked November 9, 2026, with at least two sources per species. Cautious community guidelines, not guarantees: individual fish vary. Not veterinary advice. Disagree? Tell us.