Minecraft wiki entry for Pumpkin_and_melon_farming, associated text: This farm's stacking height is 5 blocks. The second floor does not need another clock. It can take signal from redstone torch column and pass it through pulse limiter in the corner like the first floor. Items from the second floor can be sent down through first floor's water with Minecart with Hopper or chest in the water and Dropper in the Redstone circuit layer with hoppers between them.