Tutorials/Magma cube farming
Magma cube farms can be ridiculously hard to build in Minecraft. But don't give up just because you can't put water in the Nether! (except on xbox via melting ice) Here are some tips on helping you build a farm.
 Differences from Slimes
If you've built a slime farm, this will be easy. The only things different from slime farms are:
- Spawn areas
- Portal rooms
- Fall damage will not harm magma cubes
- No water in the Nether
- Tiny cubes are harmful
- May need to filter out other mobs (the piston squeezers will fix most problems)
 Spawn area
This might be the toughest bit. Find an area to spawn the magma cubes. Try checking near a nether fortress. Then build flat spawning pads, then enclose it with blocks.
 Drop holes and the reducer
Since the magma cubes blindly jump in one direction, dig some wide holes for largest type of magma cube to fall in and add pressure plates to the bottom, then link it up to some sticky pistons to crush the cube's head to cut it into medium cubes which will be crushed also. Make this one block above the plates or 2 if you need magma cream. Add some holes at the side of the plates for the tiniest cubes to fall out. If you wish to receive magma cream from your farm enlarge the output drop holes to 2 blocks high and wide for bigger cube crushing and depositing. They will fall into a portal room.
 Portal Room
Since they only jump in one direction, they can be portaled throught into the Overworld by filling the room with portals. Link these to the overworld, where you can place water. Since these mobs don't take damage from falling you don't need to care about the distance of the drop.
 The Main Farm
Once the cubes fall into the portals they can fall into a water canal system. If you let the medium cubes through, add a water grinder composed of a floor of signs with water at the top. The area where the signs are on should be hoppers that link up to a chest room, like this:
H - hoppers linking to collection room
S - sign/open fence gate
W - water
WWWWWWWWWWWWWWWWWWWWWWWWWW SSSSSSSSSSSSSSSSSSSSSSSSSS HHHHHHHHHHHHHHHHHHHHHHHHHH
Then carry the tiny cubes over to the collection room. Now start an xp farm area.
If you want this farm ONLY to do magma cubes, add a water elevator for zombie pigmen and wither skeletons etc. to transport them to a despawn tank or a separate farm or anything else that stops them interfering with your farm.