you don't need to do anything to protect it as just now as it is treated,but I would recommend that next year to clean or jet wash the flat areas(don't bother with decking cleaner, fairy liquid is just as good,honest) but do reseal the wood after it drys out(give it at least 24hrs on a dry summer night) then just use a paint roller with a reseal agent ,I use BQ's own brand CLEAR decking sealant,its about £30 for 5 ltrs but it go's a long way and is just as good as the branded products,make sure you get the CLEAR sealant,this will keep the wood with its natural colour and will only darken it very slightly,it looks dark when it go's on but don't panic,it lightens off.