Slimes are green, gelatinous blocks that come in 3 sizes, large, medium and tiny. Unlike most hostile mobs, slimes can spawn in any light level.
When killed, tiny slimes drop 0-2 slime balls. Slime balls are used to create sticky pistons and magma cream. Large slimes drop 4 xp, medium slimes drop 2 xp and tiny slimes drop 1 xp point.
When large and medium slimes are killed, they’ll split up into 2-4 smaller versions. So 1 large slime could turn into 4 medium slimes, which could turn into 16 tiny slimes. This means 1 large slime will drop between 0 to 32 slime balls and 12 to 28 xp points.
Slimes can only be found in 10% of the chunks and only in the lowest 40 levels of the map. This makes them one of the hardest mobs to find and farm.
Slimes move by hopping, which is either always in the same direction they were going, or towards a player. A clicking sound can be heard when they hop, which makes it quite easy to detect them from a distance, even through walls. Unlike most mobs, the line of sight of slimes isn’t obstructed by blocks, which means they can see through walls. If a player is anywhere within 16 blocks of a slime, the slime will move towards the player.
Unlike zombies and skeletons, slimes have a rather dumb AI. They will jump off of cliffs, into lava and water and they cannot overcome bigger blockades. They can climb ladders, but will only do so if the ladder is directly between the player and the slime. Slimes will drown in water and can be killed with fire. They also take fall damage, unlike magma cubes.
Slimes aren’t too difficult to defeat. They attack by hopping, which makes their attacks quite slow. They also don’t deal a lot of damage. Tiny slimes don’t deal damage at all, they’ll simply push the player.
The attack of slimes can be blocked by hitting them when they jump, though large slimes are hard to miss anyway. Medium sized slimes could pose somewhat of a threat in larger numbers, though walking backwards while killing them with a single swing of your sword should keep you safe.
If you really want to be safe, use a bow. The arrows will knock the large slime back and will kill the medium and tiny slimes with just 1 fully drawn shot.
Try to kill the tiny slimes last, they cannot do any damage. Though they can push you around, which could be dangerous near deep falls and lava pools, so be aware of your surroundings.
Slime balls are a much wanted item, especially on multiplayer servers. On economy servers, slime balls are often one of the most valuable items. This makes farming them a great way to obtain large amounts of slime balls in a short time.
The biggest challenge with slime farming is actually finding the slimes. They only spawn in 10% of the chunks, so it can be a real pain to find the right chunk. You then have to dig out a large room for them to spawn in and create some way to easily kill them. Luckily there are a few tools which can help you find the right chunk, some of which will simply tell you where the chunks are located when you enter a few coordinates.
Because tiny slimes cannot harm you, but will follow you, many players keep them as pets, either in seperate rooms or just as a travel companion. Do note that slimes are hostile mobs, which means they will despawn when you go too far away from them. A distance of 32 blocks or more will cause hostile mobs to start disapearing. After about a minute or so, most hostile mobs will have despawned.