Yeah bummer. Check out the Nitrogen Cycle for sure if you haven't yet.
I'd just cut some of a sponge from the existing filter and let that seed your new tanks. It speeds up things even quicker than the API product and other bb starters. Most of those are not in the aerobic state anyway.. Well actually none are haha.
Consider the surface areas you're providing the bacteria colonies to grow on within your filter. A porous rock has more colonization potential, and does not accumulate waste such as a mechanical filtration method that turns biological like a sponge...