How to Make a Kelp Farm in Minecraft

Most farms exist to feed you. The kelp farm exists to feed your furnaces. Kelp smelts into dried kelp, nine of which craft a dried kelp block — and a single block smelts 20 items, making it one of the best renewable fuels in the game. Smelting the kelp also trickles XP. This observer-and-piston design runs itself entirely: kelp grows, gets snapped, floats to the surface and lands in a chest while you do something else.

What You Need (Per Layer)

• 14+ kelp to plant
• 14+ observers
• 14+ pistons
• 14+ redstone dust
• 1+ hopper and 1+ chest for collection
• Water buckets — build an infinite water source nearby first
• A few stacks of solid building blocks; glass is optional but lets you watch it work

The observers are the expensive part early on, since each needs quartz. Everything else is iron-age materials.

How the Design Works

The trick is kelp's growth habit: it grows upward one block at a time until it nearly reaches the surface. Each kelp column gets an observer watching the spot where new growth appears and a piston aimed at the plant just below that. When kelp grows into the observed space, the observer pulses, the piston extends and snaps the stalk — everything above the cut breaks off and floats up. The plant regrows from its base, and the cycle repeats forever. At the surface, a water stream sweeps the floating kelp sideways into a hopper.

Building the First Layer

1. Dig the tank. A trench 7 blocks long, 3 wide and 1 deep. Dig a one-block channel down the centre of it.
2. Flood and plant. Fill the trench with water and plant kelp along both sides of the central channel.
3. Place the pistons one block above and one block behind each kelp, facing toward the plant.
4. Place observers above the pistons, also facing the kelp, so each observer's face watches the growth space.
5. Wire it up. Put solid blocks behind the pistons and run redstone dust along the top of them, connecting each observer's output to its piston.
6. Case it in. Build walls (glass if you like) around the tank and fill it with water to full height, making sure every water block is a source so harvested kelp rises cleanly instead of getting stuck in currents.

Adding the Collection Stream

Cap the tank with a layer at the height of the top observers, then lay water sources along one side so the surface current flows across the farm toward the far edge. Where the water lands, run a second channel one block below the farm's edge, ending at a hopper feeding a chest. Floating kelp rides the top stream, drops into the channel, and gets carried straight into storage. Wall the channel in so items can't bounce out.

Going Taller

The design's real strength is that it stacks. Build a second identical layer directly on top — new pistons and observers, kelp planted on top of the layer below's observers — case it, flood it, and route it into the same collection channel, just extended. Each layer multiplies your output without widening the footprint, at the cost of another set of observers and pistons. Two or three layers will keep a super smelter in fuel indefinitely.

Using the Harvest

Smelt kelp in a furnace — or a smoker, which does the job twice as fast for the same fuel — to get dried kelp. Eat it if you're desperate (it's a poor food), or craft nine into a dried kelp block and feed your furnaces with it. One block smelts 20 items; a double chest of blocks is effectively a lifetime of smelting. And because every smelted kelp drops a little XP when collected, emptying the furnace doubles as a gentle XP farm.