The housing thing really depends on their size.
The trio (M,F,F) I got from FishGeek are much smaller than yours, LWB. I'd say the male is maybe pushing around the 3" mark, and the females are probably more like 2.5" (total length) each. At that size, a 20 gal. would do just fine for a breeding pair. Mine still remain quite skittish even in the 38 gal. planted tank though...not sure what that's all about. Perhaps that's just their nature.
BV