Three layer moss bone meal farm

A compact three layer moss bone meal farm built for Donut SMP and vanilla Java. A lava and water generator makes fresh stone on each of the three layers, a dispenser bone meals a moss block at the bottom, and 79 pistons sweep the moss growth off. Signs, stone stairs and a short rail run carry the drops into 11 composters, four droppers return part of the bone meal to the dispenser so the farm feeds itself, and the surplus goes to a barrel and two chests. It primes on 64 bone meal and then runs continuously, and the 4,000 an hour the creator quotes is the profit after what it puts back in. Note blocks sit next to lava through most of the build, which is worth knowing before you start.

Bone meal the moss block next to the bottom piston by hand before you switch it on. Starting it with no moss placed is what pushes the bottom piston out of position and wrecks the farm, and MopsicleDev, ADG3000 and t0m1kx-1 all land on the same fix.
The note blocks catch fire from the lava opposite them. Put stone buttons on them until the video tells you to cap them with a block, or punch the fire out, the farm still works.
Half the composters sitting idle is normal. ADG3000 says the extras are overflow capacity and the farm is not fast enough to fill all 11.
If it starts making cobblestone, mine all of it out, put stone back, and check that no stone has generated where the lava belongs. Piddledingle26 had to do this three times after a friend unloaded the chunk with the farm running.
On a laggy server, dalukiz sets the two repeaters on the clock that the tutorial never touches to 2 ticks.
If you modify the farm, take the items out of the hoppers at the bottom, t0m1kx-1 found they cap how much it can make.