That is exactly how I do it! Rinse it out and put it back in the filter. My thoughts are I want to remove any uneaten food / bio waste BEFORE it breaks down into Ammonia -> Nitrites -> Nitrates by rinsing it out of the mechanical filter media. This is why I prefer sumps, because it is MUCH easier to pull, rinse and replace mechanical filtering media in sumps than it is in a canister. In my opinion this is also a very big advantage of hang on back filters over canister filters.