You should wait until the pup is 1/3 to 1/2 the size of the mother plant. Carefully cut the pup away from the mother down at the roots. Take a little root with the pup if you can. Eventually the mother plant will die off naturally, so you may want to leave one pup to take it's place, so you don't end up with a bald spot.
-----
Ken
Peace of the Tropics
www.PeaceOfTheTropics.com
Bastimentos pumilios
Blue jean pumilios
BriBri pumilios
Intermedius
Lamasi
Imitators
Ventrimaculatus
Fantasticus
Aurataenias
Vittatus
Tricolors
Auratus
Red trivitattus
Green trivitattus