Sex Tank Question

[MrKrabs]

What size tank is best to get a trio of guppies (1 male 2 females) to mate?
The females are too fast in the larger 20 gal tank. My male has a large tail fin and so is pretty slow in comparison. Would a 2.5 gal or 5 gal tank work? I wont see them mating but how long do you think it will take til I can return them to the larger tank? Thanks

[lohachata]

a 5 gallon would be fine.