Hi, I have been running a fx5 on my ray tank for approx 6 weeks now and i have had a look inside the filter a couple of times to check if its dirty and the sponges are more or less still spotless? I only have 2 motoro's which are around 6 to 7 inches and im doing 25% water changes twice a week. So my question is why is my filter still spotless? Oh i have been dosing seachem stability for the past week.