About This Guide

A high-yield guardian farm built inside a drained ocean monument. Guardians spawn in the dry chambers, get pushed by water currents to a drop shaft, and die in a kill chamber below. Produces prismarine, sea lanterns, and fish passively — one of the best XP farms in the game. This advanced mob grinder build works in Minecraft Java Edition, version 1.20+ and above. Budget around 60-90 minutes for construction — have all materials in your inventory before you begin.

Difficulty: Advanced

This is an Advanced build. It demands solid familiarity with at least one of Minecraft’s complex systems — redstone timing, mob AI behavior, or intricate 3D spatial layout. Gather every material before placing the first block, and expect to debug. The payoff in automation, efficiency, or aesthetics is well worth the effort.

Materials You’ll Need

Material	Quantity
Sponge	20
Stone Brick	128
Glass Block	64
Water Bucket	16
Hopper	4
Chest	2
Cobblestone	64
Slab (any)	8
Potion of Water Breathing	5
Night Vision Potion	3

Total distinct materials: 10. Gather everything listed above before you start — mid-build supply runs break your momentum.

Step-by-Step Instructions

Step 1: Find and Mark the Monument

Locate an ocean monument (use an explorer map from a cartographer villager). Mark its corners with pillars of dirt or sand above the water. Drink potions of water breathing and night vision before starting — you'll be underwater for a long time.

💡 Tip: Kill the three Elder Guardians inside first. They inflict Mining Fatigue which makes construction nearly impossible.

Step 2: Build Collection and Kill Chamber

Below the monument floor, excavate space for a kill chamber and collection system. Place a chest with hoppers feeding into it. Build a cobblestone-walled kill platform with slabs at viewing height. This is where guardians will die from fall damage.

💡 Tip: Guardians need a 24-block drop to take lethal fall damage. Build the drop shaft before draining the monument.

Step 3: Drain the Monument with Sponges

Fill the outer walls of the monument with stone brick, sealing it off. Use sponges to absorb all water inside (sponges absorb 7x7x7 area of water — bring many). This is the most time-consuming step but is essential for guardian spawning.

💡 Tip: Dry sponges in a furnace to reuse them. You'll need to cycle through 10-20 sponges multiple times to fully drain the monument.

Step 4: Add Glass Viewing Walls

Replace the middle row of walls (at eye level) with glass blocks on all sides. This lets you watch guardians spawning and verify the farm is working without entering the chamber. Guardians cannot break glass.

💡 Tip: The glass row lets you debug spawn issues without opening the farm. Essential for diagnosing low spawn rates.

Step 5: Install Water Push Channels

Inside the dry monument, place water source blocks to create channels pushing guardians toward the central drop hole. Water should flow from all corners toward the center. Guardians can swim but water currents overpower them and push them to the drop.

💡 Tip: Experiment with water placement to eliminate dead spots where guardians get stuck. Every guardian must reach the drop.

Step 6: Activate and Collect

AFK at the kill chamber. Guardians spawn inside the monument, get pushed by water to the center hole, fall down the drop shaft, and arrive at one-hit health. Prismarine, sea lanterns, and raw cod accumulate in your chest automatically.

💡 Tip: Guardian farms are the fastest source of prismarine and sea lanterns. A well-built one produces thousands per hour.

Tips & Tricks

Kill the three Elder Guardians inside first. They inflict Mining Fatigue which makes construction nearly impossible.
Guardians need a 24-block drop to take lethal fall damage. Build the drop shaft before draining the monument.
Dry sponges in a furnace to reuse them. You'll need to cycle through 10-20 sponges multiple times to fully drain the monument.
The glass row lets you debug spawn issues without opening the farm. Essential for diagnosing low spawn rates.
Experiment with water placement to eliminate dead spots where guardians get stuck. Every guardian must reach the drop.
Guardian farms are the fastest source of prismarine and sea lanterns. A well-built one produces thousands per hour.
Light up all caves within 128 blocks of the farm to maximize mob spawning rates inside your structure.
Take a screenshot of the finished build from multiple angles — you’ll thank yourself when you want to recreate it in a future world.
Label a nearby chest with a sign so you can dump leftover materials immediately and keep your inventory clean.