I need help because I want to build a slime farm I have found chunks using a slime chunk finder. I have built it below level 40 at 14, It's a 16 by 16 area and I have triple checked my coordinates -177 -833 to -192 -848 and seed 5545643967389872387 using this website. . I have placed jack o' lanterns spaced out on it. It is in fact 3 blocks tall. I at one point left the area more than 25 blocks away and less than 40 for about 4 hours! and not a single slime has spawned. What can I do or what am I doing wrong.
01 Answer
First, ChunkBase is NOT considered official nor trusted (This has been repeated over and over and over again on Mojang's bug tracker) means to determine where slimes will spawn (source: Mojang Bug Tracker) That aside, Large slimes require 4 blocks, and I would recommend 5 for good measure. Third you need to be 32 blocks away for them to spawn. Finally, mob cap, you may need to kill mobs within several chunks distance and light all cave as well.
Understanding how mobs are spawned helps a lot. The game determines a spawn location, then decides what to spawn, if valid spawn it checks space available, light levels, mob slots, and world/y-coordinate. Then, for certain mobs, it re-rolls to determine whether or not selected mob will actually spawn. For slimes, we do have a re-roll which causes a very low spawn rate (Source: minecraft source code). Move 32-120 blocks away along x-z axis. In this area kill all mobs, including bats.
In addition to slime chunks, slime spawn in swamp biomes on the surface, more so on full moon (or is it new moon?) but equally under ground as slime chunks do.
Another factor to consider is what version of the game you are playing. If you check the bug tracker you will find that Slimes periodically stop spawning in certain versions of the game. I can confirm that they do spawn in the most current version.
As this question has been asked and answered I would suggest your read here as well : Why aren't any slimes spawning in my slime farm? --
