A decent quantity of quality LR will provide pods for your system. As long as the system is stable and predators are limited they will reproduce at a fairly rapid rate. You can purchase them from a few sources...but I prefer to get mine from the rubble/crud at the bottom of large tanks used to cure LR. I know of a LFS that always has a large amount of LR curing and they normally will let me get a few lbs of crud from the bottom for free.