in my veg room i run a huge rez with the trays on top.and i cannot open it with out removing the trays,a easy way around this is 2 buy a half inch grommet and a 1/2 inch on off valve.drill a hole in the center of the rez and whalaaa u have a sample port to take your readings,open it up and pour your sample into a glass,check your ph and tds right there,if u need to make corrections pour the addiditives into the tray and it will go right down into the rez:thumbsup: