well i have my male and female in a 20g.. but i moved just the female to a 5g till the fry came then moved her back.. if your going to leave them in the same tank i heard a 20g is fine
I have 2 20gal guppy tanks, swap out the little ones when they get big enough to the adult tank, use a breading box in the other tank that holds 5 dividers and I put in 2 pregnant females in each, the setup makes enough for my 55gal cichlid tank with 15 cichlids.
like stated above, separate tanks for the fry are essential. if you leave the fry in with the parents then the water quality will quickly deteriorate unless u do alot of w/c because of all the fry. a 10g for parents and a 30 for fry is the minimum in my opinion. ime, platies are better. bigger fry, more fry, and they grow allllllottt faster