I have an SPS tank and in my sump had a bunch of filter pads. I thought the same thing after seeing all the gunk that it would take out of tank. Everytime I would clean out the filter pads i would get nasty gunk even after 4 days. I eventually took them all out and learned really its just a collection for phosphates that leach back out into the system. I thought that for a minute it would lead to dirtier water without the pads but as i learned my water is now more clear and with less phosphates. I now just run my skimmer, carbon, and GFO. I used to get tons of skimmate and now since i removed the pads it only skims after i feed. IMO i would ditch them, its all a matter of preference.