how long to gan some bacteria

[LMOUTHBASS]

ok in preparation of a 3 gal q tank i will be setting up shortly i cut a small piece off of my extra AC sponge i have and put it in my AC500 to collect bacteria - my AC500 has only been on my tank for about week n a half - so i doubt there is much bacteria in there yet - although the tank is cycled and has another older filter running on the other side of the tank - (penguin)
so
how long shoul i leave the extra piece of sponge in there ?
i plan on putting it in the filter of my little tank to instant cycle it but wanna make sure i have enough bacteria on it
i'm thinking a month shoul be sufficient

[tomm10]

I hear 3-4 thrown out there a lot for time frames.

[JSchmidt]

A month would be good. That should give you a good starter culture of bacteria.

HTH,
Jim