Replacing Filter Cartridge That's Falling Apart

[`Peter]

So here's the deal, established tank for over 13 months now and I have a Penguin Biowheel filter that can hold two cartridges. One of the cartridges is literally falling apart after washing and cleaning it after most water changes. I t really restricts my water flow with me running co2 on a planted tank which is not good at all. I want to replace it with a new one but last time I did it I guess I took away enough bacteria that my nitrite readings spiked up and I had to do a huge water change. I'm glad none of my fish died back when I did this months ago but I could tell they felt the effects.
 
So how would I go about the process to replace the cartridges/pads? Would I just rip off the existing ones with the bacteria and stuff it along with the new cartridge while waiting for the bacteria to spread to the new one. If so, how long should I wait to be certain so this happens? Any tips or feedback is appreciated

 

[Mamashack]

Wish I could help Peter, but I have no experience of this type of filter. Mine is a simple submersible sponge one so only needs rinsing every water change. Hope someone else can help out.

 

[Mikey1]

the reason why there is two cartridges is so you can replace one at a time alternately,
 
never replace both at the same time,
 
there should still be enough bacteria left in the one cartridge and bio wheel,
 
you should never need to clean the bio wheel, just leave it alone, you might want to remove it once in awhile to clean any scum/algae off the filter around the bio wheel, but you should never have to rinse or clean the wheel itself