The short answer
A 60 litre (about 15 gallon) tank suits a group of 6 to 8 adult guppies as a starting stock. Guppies are small but active and, crucially, breed relentlessly, so the real question is less about adults and more about managing fry. If you keep both sexes, use a ratio of 2–3 females per male so no single female is constantly harassed.
Why the ratio matters
Male guppies chase females almost non-stop. With one female per male she gets no rest, which stresses her and can shorten her life. Keeping several females per male spreads that attention so no individual bears the brunt. An all-male group sidesteps the issue entirely — you get the colour without the fry explosion. Either works; a single male-and-female pair does not.
Sensible 60 litre guppy stocking
- 6–8 males only for pure colour and no fry
- 2 males + 5–6 females if you want a breeding colony (expect babies fast)
- Guppies plus a cleanup crew: nerite snails or amano shrimp
- A small peaceful tankmate group such as harlequin rasboras if you keep guppy numbers modest
Avoid packing in more just because they’re small — a fast-breeding tank overshoots its filter quickly.
Before you stock
Cycle the tank first — see how to cycle an aquarium. Read the full guppy care guide, sort the ratio with how many female guppies per male, and check whether you can mix them using can I mix tetras and guppies. For the tank itself, see the best 60 litre aquariums.