Right ok ill do my best to answer both in as much detail as possible.
1) my filter is a juwel bio flow 3.0 I'm not sure on its turn over rate but I have 125L tank
2) and I meant replacing all the media inside the filter, the coarse and fine sponges the carbon, nitrax and the poly pads. I have cleaned my poly pads using a little tank water to get rid of some of the bits but they're looking kind of dirty brown colour now.
If I'm replacing any sponges/carbon should I do it in stages, what I mean by this is week 1 replace fine sponge, week 2 replace coarse, week 3 carbon and so on so that I don't lose all good bacteria that's in there