Want to change out media in established filter
So I have three 5g minibows with a betta and a few nerites in each. Each tank has a Hagan Elite Mini Internal Filter in it: http://www.amazon.com/Hagen-Elite-Underwater-Filter-Listed/dp/B0009YD7D4
All the tanks have been up and running for anywhere from 6 months to 2 years, so the filters are well established. However, 2 of the filters contain the wrong media in them - the proper media is simply a small square sponge that fits the filter perfectly. Now, I've had these filters for many years with many bettas, and at some point the media on 2 of them got tossed - probably cause a fish died of something nasty and I just tossed out everything in the tank. So I have some junk media stuffed in 2 of them but I don't feel it's doing a good job. I bought some nice sponges today and I'd like to use them in these filters, but I'm not sure how to do this without disrupting the cycle.
There may be room to keep a tiny bit of the old media in with the new sponges, but I'd be losing most of it. And I will be squeezing the heck outta the old stuff to get the bacteria into the tank and onto the new sponges. But will it help to toss the old stuff (just floss and odd bits of sponge) into the tank itself and just let it lay around on the bottom for a while? Any other suggestions?
If there's no way to do this without disrupting the cycle then I simply won't do it.