What are the important, bacteria-loaded parts in my filter?

So in my Fluval filter there is a bio foam pad in the bottom basket, the bio rings in the middle basket, activated carbon in the top basket, a pre-filter pad in the side slot, and a "polishing" pad.

Which of these things is the part (or parts) I need to leave in there when replacing them so that bacteria can transfer from the old to the new?

 

If I were you I would only replace the carbon and polishing pad.

 

bio foam pad important, rinse in used tank water, replace only when falling apart
bio rings most important, don't do anything but rinse in used tank water
activated carbon not important, many fishkeepers don't use carbon, good for removing meds from tank
pre-filter pad important, rinse in used tank water, replace only when falling apart
"polishing" pad somewhat important, rinse in used tank water, replace only when falling apart


Which of these things is the part (or parts) I need to leave in there when replacing them so that bacteria can transfer from the old to the new?

response in red

 

Lynda, Great reposnse except...I believe that the polishing pads in the Fluval need to be replaced. They are actually only good for a very short amount of time (depending on water conditions it could be a few hours to a few days) until they become clogged, and they are so dense that they don't rinse out properly. So for those reasons I choose not to use them in my Fluval.

 

Great response Lynda.

But I have to agree with JD. If you can manage to rinse a fine filter (polishing) pad, and still get it to fit without ruining it, by all means keep it, but I struggle.

And here's my scientific view on it - most of your beneficial bacteria is in the pre-filter, bio-rings and foam pad. If we keep this in mind, by the time the water gets to the polishing pad, there will be little (if any) nitrogenous waste for bacteria, so the polishing pad really just polishes and can safely be replaced (mine gets changed every 2-3 months, but your mileage will vary).

 

Thank you both for correcting my thoughts on the polishing pad.