I AM A TREX CONTRACTOR.YOU DONT HAVE TO PUT ANYTHING ON TREX TO MAINTAIN ITS COLOR OR LONGJEVITY.BUT!,YOU DO HAVE TO CLEAN IT ONCE OR TWICE A YEAR USING A CHLORINE BASED DECK CLEANER. THIS KILLS THE MILDEW.DO NOT EVER POWERWASH TREX, THIS WILL SEVERLEY ENHANCE THE MILDEW GROWTH.ALL COMPOSITES MILDEW IN THE SAME WAY. THIS WILL NOT HARM THE PRDUCTS.IF YOUR HOUSE WAS GLASS IT WOULD STILL GROW MILDEW ON THE NORTH SIDE.SO THEREFORE CLEANING TREX OR OTHERS SHORE BEATS STAINING, CRACKING AND WARPING AND SPLITTING.WASH A TREX DECK 20 YEARS FROM NOW AND IT STILL LOOKS THE SAME. WASH A CEDAR DECK 20 YEARS FROM NOW AND ITS STILL AGED GARBAGE.CRACKS ,SPLIT,WARPED AND ROTTED.IF IT EVEN LAST THAT LONG!