Why does my Minecraft mob farm not produce?

September 18, 2011 3:41 PM

I built a mob farm in Minecraft but its output does not seem to be nearly as great as the tutorial implies. Did I mess up or are my expectations just too high?

I followed this tutorial almost exactly to the letter. I made sure to measure all distances carefully to ensure that the water flowed correctly with no dead spots. The only deviations I made from what is described on that page are:

1. I had to insert a couple of 90 degree turns in the canal post-lavablade (the part the only carries items) to work around a lava pool. I made sure to have at least two squares on both sides of the elbow before changing elevation, as the tutorial mentions.
2. Where the 'main' (central) canals meet the edges of the room (i.e. where they start at a depth of 2) I made a one-block step cutout on both sides so that I could get in and out easily without fighting the current. I didn't think this would matter as most of the canals start at depth 1 anyway.

The tutorial suggests that items will be plentiful, even going so far as to say there will be items waiting for you by the time you finish extinguishing all the torches and sealing off the room and getting down to the collection point. This was not the case for me. In the video mentioned on that page at about the 5:30 mark the author shows how fast he gets items from his farm and says that inventory will fill up in about an hour. Mine is nowhere near that fast; they only occasionally trickle in. I've idled at the collection point for over 6 hours and all I have to show for it is approximately 15 units gunpowder, 30 bones, and 50 arrows. Based on that video I thought I'd be swimming in TNT in no time, but after all that work I only have enough to make a few.

So that leaves me thinking that there are several possibilities to explain what's happening:

1. Some light is leaking in the room, or I missed one or more torches. It seemed pretty dark in there, but I suppose there's a chance I missed some. Can I just temporarily set the difficulty to friendly and go in there to check?
2. The game parameters of 1.7 have changed since that video and tutorial were made, making this device inherently a lot less effective (why wouldn't someone update the wiki to mention this before I spent all those hours digging?!?)
3. The third option -- I did something else wrong but I don't know enough about the game to know what.

posted by Rhomboid to Sports, Hobbies, & Recreation (11 answers total)

I vote for option 3: did you change the difficulty level to "hard"? The mob grinder works best when lots of monsters spawn.
posted by knz at 4:23 PM on September 18, 2011

Version 1.8 broke mob farms. The spawn rates for all mobs are much lower than they used to be.
posted by empath at 4:36 PM on September 18, 2011

Can I just temporarily set the difficulty to friendly and go in there to check?

Sure.

But I would bet that your problem is either:

(1) There are lots of monsters spawning elsewhere in your spawnable space. Look at your map in minutor or similar and look for caves near your trap.

(2) You put your idling location too close to the spawning floor, so that some of it is in the unspawnable space surrounding you.
posted by ROU_Xenophobe at 4:37 PM on September 18, 2011

Also, enderman break mob farms if the ceilings are high enough to spawn them.
posted by empath at 4:37 PM on September 18, 2011

Oh right, yeah you have to light up all the caves underneath it and all around you, also or else mobs will spawn down there.
posted by empath at 4:40 PM on September 18, 2011

Response by poster: The difficulty is already set to high. I'm playing 1.7. I don't know what an Enderman is, but the wiki page says that the design does not need to be modified to work with them. I put the idling location exactly where the tutorial said to.

I downloaded and ran minutor, and this is what it looks like around the farm structure. I know that I've run into (and lit up with torches) some of those caves, but certainly not all. How far out from the farm do I need to go in this search?
posted by Rhomboid at 5:14 PM on September 18, 2011

Are you standing there waiting for mobs to spawn? You may be too close. Go stand ~50 blocks away for a while and see if that helps.
posted by mudpuppie at 5:25 PM on September 18, 2011

F3 will be of use here, because it will show mobs as numbers. I used it to diagnose some problems I had. Notably, my problems were these:

* I was too close to one edge of the spawning room, or something. A lot of the creatures could sense me and would head in my direction, and basically stick around bobbing in the water not going down into the killing area. Moving further away fixed it.

* I didn't clear out all the places for monsters to spawn - the trap would work for like 10-20 minutes and then would stop producing. If I looked around with F3 I could find clusters of monsters - if I head in that direction I'd usually find either a spawner or a little cave with some monsters spawned in it

Fixing these helped - but still I don't get the spawn rate I've seen in some videos. I'm playing in a multiplayer server though, the rules may be a bit different.


The area around you that needs to be cleared can be Quite Large. If you find F3 cheating you can try my other method - make a grid topside and drill down, I used a 20 square grid. That is, I'd go all the way to bedrock, then come back up, go over 20 blocks, and do it again. I basically just made a huge grid doing this and would intersect with most of the caves in the area. Very tedious. When I found out F3 could find mobs at a distance I switched to that.
posted by RustyBrooks at 7:01 PM on September 18, 2011

You might find something of use in this video. It seems that there may be a bug in Minecraft that prevents mobs from spawning.
posted by Solomon at 11:45 PM on September 18, 2011

Response by poster: Never mind, it doesn't matter. I'm done with this game. Lose power while you're playing and your whole world is gone, that's some great coding there. Tried these instructions to recover, but like the transporter in The Fly, it came back all wrong, garbled and distorted; crashes trying to play the recovered level.
posted by Rhomboid at 2:17 PM on September 19, 2011

There's several things to consider here:

1) is there anywhere else nearby that can spawn mobs. Minecraft has a maximum number of mobs that can be on the map in the game at any one time, so if your mob grinder is the only place they can spawn, they'll spawn there and in big numbers. I get much more items in my mob grinder at daytime rather than at night for this reason.
2) Are you standing too close? No mob will spawn within 32 blocks of the player (though plenty will spawn just outside). If I walk away from my mob grinder and back again, I will find a lot more items than if I just hung around at the collection points because of precisely this reason.
3) Because you have got some items (just a lot lower than you were expecting), you've almost certainly built it correctly.
4) Does it need to be bigger? I built my mob grinder based on this - http://www.kevblog.co.uk/how-to-build-a-minecraft-mob-grinder/
5) Don't worry too much about Endermen. Yes, they can pull blocks out and make it less effective (or even stop it working completely, but this is less likely). However, they are rare, they will hurt themselves when they fall in the water streams, and most of the time they will only ever expose the cave to light, making mobs spawn less. However - this kind of damage is generally pretty obvious.
posted by BigCalm at 7:43 AM on September 26, 2011