How to Build a Guardian Farm in Minecraft

Guardian farms are among the most rewarding builds in Minecraft. They produce prismarine shards, prismarine crystals, raw cod, and solid XP. The challenge is that guardians only spawn inside ocean monuments, so building the farm requires draining or modifying a monument structure. This guide covers the full process from locating a monument to running a high-output guardian farm.

Why build a guardian farm?

• Only reliable source of prismarine blocks and sea lanterns.
• Excellent XP output (second only to the Enderman farm).
• Produces raw cod as a food byproduct.
• Once built, it runs passively with no player input required.

Materials list

Item	Quantity	Notes
Sand or gravel	10,000+	For draining the monument
Sponges	60+	Obtained from elder guardians inside the monument
Building blocks	3,000+	For the perimeter walls
Soul sand	64+	For bubble columns
Glass or glass panes	200+	For the kill chamber viewing area
Hoppers	20+	For collection system
Chests	10+	Storage
Water buckets	~50	For creating water streams and bubble columns
Magma blocks	64+	Alternative kill method
Signs or open fence gates	50+	Water flow control

Step-by-step build instructions

Step 1: Locate an ocean monument

Ocean monuments spawn in deep ocean biomes. Use the command /locate structure minecraft:monument if cheats are enabled, or brew Night Vision potions and scan deep ocean biomes by boat. Monuments are large dark structures on the ocean floor made of prismarine blocks.

Step 2: Defeat the elder guardians

Each monument contains three elder guardians. They inflict Mining Fatigue III, which makes block breaking painfully slow. Kill all three before you start any construction. Bring a Sharpness V sword, strength potions, and water breathing potions. The elder guardians are located in the top chamber and the two wing chambers. Each one drops a sponge, and the sponge rooms inside the monument contain more. Collect every sponge you find.

Step 3: Build the perimeter

The guardian spawning box extends 58 blocks in each direction from the monument center horizontally, and from Y=39 down to the ocean floor vertically. To maximize rates, you need to prevent guardian spawns outside your farm. Build a solid wall (or use sand) around the entire monument at a radius of about 60 blocks. This wall needs to extend from the ocean floor to above the water surface.

Top-down perimeter view:

  +---------------------------+
  |                           |
  |      WWWWWWWWWWWWW        |
  |      W  MONUMENT  W      |
  |      W    xxxxxx   W      |
  |      W    xxxxxx   W      |
  |      W    xxxxxx   W      |
  |      WWWWWWWWWWWWW        |
  |                           |
  +---------------------------+

W = Perimeter wall
x = Monument structure

Step 4: Drain the monument

This is the most time-consuming step. There are two main approaches:

Sponge method: Divide the interior into sections using temporary walls (sand columns work well). Place sponges inside each section to absorb the water. Smelt the wet sponges in a furnace to dry them and reuse. Work section by section, top to bottom.

Sand/gravel fill method: Drop sand or gravel to fill the entire monument interior, then dig it out. This is slower but does not require sponges. Many players use a hybrid approach: sand columns to create sections, then sponges to clear each section.

The entire spawning area inside the perimeter needs to be drained. Guardians cannot spawn without water source blocks, so once drained, you control exactly where they spawn.

Step 5: Build the spawning layers

Inside the drained perimeter, create spawning platforms. Guardians need water to spawn, so place water source blocks on flat platforms spaced 3 blocks apart vertically. Each platform should have water flowing toward a central channel. Use signs or open fence gates to stop water from flowing into areas you want dry.

Step 6: Create the collection system

Water streams on each spawning layer push guardians toward a central drop shaft. At the bottom of the shaft, place either:

• Magma blocks for a fully AFK kill (guardians take damage from magma). Place hoppers under the magma blocks to collect drops.
• A fall damage tube with a 23+ block drop. Guardians have 30 HP (15 hearts), so a 34-block fall kills them outright.
• Bubble columns using soul sand to push guardians upward, then let them fall. This concentrates them in one spot.

Step 7: Build the collection and storage area

Below the kill zone, place a grid of hoppers feeding into chests. If using the magma block method, the hoppers go directly under the magma. For fall damage or campfire kills, place hoppers at the bottom of the drop shaft.

How it works

Guardians spawn exclusively inside the bounding box of an ocean monument. The game checks for water source blocks at the spawn location and sufficient space for the guardian's hitbox. By draining everything outside your spawning platforms, you force all guardian spawns onto your controlled layers. The water streams then funnel them to the kill zone.

The hostile mob cap (70 in singleplayer) applies to guardians. Since your perimeter prevents spawns outside the farm, the entire mob cap fills with guardians inside your farm, maximizing rates.

Efficiency stats

• Prismarine shards per hour: 3,000-6,000
• Prismarine crystals per hour: 1,000-2,000
• XP per hour: ~50,000 (with player kill)
• Raw cod per hour: 1,500-3,000

Common mistakes

• Incomplete draining. A single leftover water source block outside your platforms can steal spawns. Use sponges methodically and check every corner.
• Perimeter too small. If the perimeter does not cover the full 58-block spawning radius, guardians spawn outside and waste mob cap slots.
• Forgetting elder guardians. If even one elder guardian survives, Mining Fatigue makes the entire project miserable. Kill all three first.
• Standing too far away. Mobs only spawn within 128 blocks of a player. Position your AFK spot so the entire farm is within range.
• No lighting on the ocean floor. Drowned and other hostile mobs spawning near the monument eat into the mob cap. Light up or slab the surrounding area.

Frequently asked questions

How long does it take to drain a monument?

With sponges and a helper, expect 4-8 hours of real-time work. Solo without sponges (using only sand), it can take 10-20 hours. The payoff is worth it.

Can I build this on a multiplayer server?

Yes. Guardian farms work on servers. The main concern is that other players loading chunks near the monument can cause guardians to spawn outside your farm. Coordinate with your server community or build far from spawn.

Do I need Silk Touch for the sponges?

No. Sponges drop as wet sponges when broken. Place them in a furnace with any fuel to dry them. You can also place wet sponges in the Nether, where they dry instantly.

What can I do with all the prismarine?

Prismarine shards craft into prismarine blocks, prismarine bricks, and dark prismarine, all popular building materials with a unique sea-themed appearance. Prismarine crystals combined with shards craft sea lanterns, which are light-level-15 light sources that work underwater. Sea lanterns are also one of the only light sources that pair well with underwater builds. The excess raw cod can be cooked for food, composted for bone meal, or sold to fisherman villagers for emeralds.

How does this farm compare to an Enderman XP farm?

The Enderman XP farm is faster for pure XP (30+ levels per minute vs roughly 10 levels per minute for a guardian farm). However, the guardian farm produces vastly more valuable block drops. If you need prismarine and sea lanterns, the guardian farm is irreplaceable. For raw XP speed, the Enderman farm wins. Many players build both and use them for different purposes.

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