Minh -
The 100 microns are pleated paper filters. I have a back up set. I replace once a month and bring them back to the shop where they are pressure washed,soaked in a trash can with a 15% bleach solution, followed up with de-chlor bath.
The 25 microns are nylon and clean very well with a pressure wash and are replaced immediately after washing.
Replacing the four cartridges, two at a time, takes about an hour to an hour and half. Cleaning out the cannisters themselves is very important too.
I DO NOT wholeheartedly agree with what people have said in this thread about cannister filters removing necessary particulates for filter feeders. The owner of this aquarium literally uses over a gallon a month of Reed Maricultures Phyto Feast Live and Roti Feast, both being target fed.
An overkill? Yes in my opinion. But the aquarium is always clear.