I'd just make sure it's as long as possible from a water change & stir up the substrate a bit, getting some junk in the filter pad to seed it.
I have a Cascade 300 and a AC 30 running on one of my 55 tanks, but instead of using those disposable filter pads, I replaced them with a sponge (AC 110 sponge) cut to fit inside. I also put on the bottom of each of the filters some matrix, that way I am getting the best of both worlds from my HOB....I have to thank RICHE for this idea...
Yes, ideally you would want two filters running on any given tank.(or other tanks/filters to steal BB from) That way you can wipe out the Bio on one without risking crashing the tank.
But, telling the OP what you have going does not help their question /situation.
(Sorry for being a Koch, but...) Should my original reply been... "I have 30+ tanks running, I just tank BB harboring media & seed the new tank"? No
Steve, I'd suggest giving you a dirty bomb from one of my sponges. But, IMO all that will do is clog up your new filter cartridge & leave you having to buy an another new one.
So, I'd just use the method I posted above & keep an eye on parameters.