Congratulation Morten, very fine filter (i suggest you're talking bout EHEIM canister filter). The best on it is the very long lifetime with minimum noise. My oldest is more than 12 years old and get a little noisy now (think i must change the magnet wheel for the first time). I myself use 3 of them for my bigger tanks (>100 L). Using the by eheim recommended material layer (what i do) is ok !! Long standing time up to 1 year with very fine biological nitrification (no nitrite no ammonia since using it). No need to waste filter material after use - just clean and reuse it. To elongate standing time (when water flow goes down to early) it's possible to flush it with wasted water on water change. Therefor i put filter into douche, remove head and first filter layer and flush the left filter material with a few buckets of the wasted water. After that clean or exchange first filter layer and get it back to work. Newly i saw specificly designed filter sponges for eheim filters in different sizes and 2 types of porosity - never tried until yet but sure will do on the next filter cleaning. I will use them as last layer (on top). Thomas