Cycling a Filter in an Established Tank

[Kiara1125]

I'm currently doing this, but how long approx. would it take to cycle?? Before I get my Betta, I'm going to use the tank as a birthing tank. Hopefully, this will prevent Misery from getting streesed out and aborting her babies...again. The mix of Platies is gonna look cool, but I need an answer so, if you think you have an extimation, let me know!!*crazysmil