Hello i just recently built a creeper farm but spider clogg up the system.How do i prevent them from spawning? I cant use carpets,because i am using a water based farm.I tried walls in the floor,but that got the creepers stuck. How can i stop spiders from spawning without blocking the creepers?
The only thing I can suggest to you is pressure plates, however, this may disrupt your water flow trapping creepers in the gaps. Mobs cannot spawn on redstone components. Open fence gates won't work because mobs can spawn in open fence gates. Signs for the same reason.
if you make every other floor block a bottom slab spiders wont spawn like:
viewed from above
of course this will also cut your creeper spawn in half.
This wont work. Spiders can spawn in any open 3x3 area as long as there isn't any obstruction. They can even spawn on a single block as long as there isn't any obstruction in a 3x3 area. (They also need ~2 blocks high of space)