I pretty much use a double layer in my drip tray. It catches tons of debris, usually tons of silt trapped in it. I buy the roll that looks like a kids sleeping bag.
japanese matt is the only thing i buy and use other than the
free pads from fluval that are included in the fx5/6's that are
almost always included weather you buy it new or used. any
other ones ive tried clogged way too fast.