If you want to, you don't even have to run the two at the same time. Just remove the media from your internal canister and stuff it in the media chamber of your new filter. As long as water is flowing through it, the bacteria are doing their job. Placing the established media directly upstream of the biowheel should help seed it as well. Consider getting a filter that doesnt' use replacable cartridges or try just using sponges designed for other fitlers. it will drop your filter maintainance cost to.....ummmm.....multiply by two.......carry the one........$0.00.
In my eclipse I just stick a filter sponge from a fluval 104 in the filter chamber. I place a filter bag with 100% polyester quilt batting from walmart next to it in order to polish the water (its the same stuff as filter floss).
