Because it looks likely I'll be dosing my fish tank with Levamisole or another anti-biotic, I need to be prepared to remove the carbon filters so the medicine isn't all sucked out of the water too soon. However, I'm a little confused by what part of the Fluval 2-plus filter pads are considered carbon pads. My filter has three sponges, the one in the middle being a polyester wool pad that is replaced every four or so weeks, the other two foam pads rarely ever being replaced (only replaced one since 2009). Now, obviously I don't remove them all - that'll be very bad for the fish, since they need something that gets rid of ammonia and nitrites - but is it the middle sponge, the polyester wool one? My two other sponges (the foam pads) are not the black carbon pads that are available for this size filter (which I have previously assumed are for specific purposes, such as removing medicine, etc, and not general use).