Not surprisingly, you have gotten several different answers on what to put into your canister filter.
What you put into your canister filter, the cleanup crew you select, whether or not you use a skimmer all depends on your approach to aquarium keeping.
I personally prefer a low tech approach that is very freindly to small invertiebrates. It includes live sand with a plethora of small animals to consume and process detritus, no skimmer and macro algae for nutrient export.
I have very little detritus in the main tank because it is all food for other critters including: amphipods, copepods, bristle worms, feather dusters and many other small invertibrates.
I avoid hermit crabs and shrimp because they are opportunistic omnivours that would consume all the life in my sandbed that processes detritus.
More typical setups would usually include a skimmer to remove organics from the water column, adsorbants like carbon, chem-pure, phosban etc. and possibly mechanical filtreation like a sponge.
The issue with a sponge is that the detritus it traps becomes colonized by bacteria very quickly. The bacteria break down the detritus releasing nutrients like nitrate and phosphate back into the water. That is why I suggested that you need to clean a sponge several times a week.
As for cleanup crew, the best all around cleanup crew is the ever present, butt-ugly bristle worm. Ofthe snails, those that come as freebies on live rock like stomatella varia are the most hardy species.
This is all kind of general but hopefully it gives you an overview of how to approach your tank.
Fred