Hi, in a realm I used Gnembon's tutorial to build a mob farm in a deep ocean with 10 spawning floors starting at
Y = 65 and up to Y = 92.
I have the roof at y = 96
I have AFK-spot at Y = 146 and one at 191, but if I go afk for a bit i haven't gotten any loot at all. But when i fly around it a lot of mobs spawn. What is the optimal afk height? Do i have to light up the caves around even though its deep ocean?
Can it be due to a poor redstone clock? That they fall down to Y = 8?` That I'm standing at the same block and not moving around?
If you are at Y=146 and drop the mobs towards Y=8 then they will despawn at the latest as they pass Y=18, you need to stay within 128 blocks of the whole mob farm, from the spawning platforms to where the mobs are killed.
For maximum spawns you should afk more than 128 blocks above the ocean to keep drowned from eating into the mob cap, but then the farmed mobs also have to be killed above the ocean so they stay within 128 blocks of you.
Caves within 128 blocks of your afk position should be lit up.
If you don't want to rebuild the spawner you should kill the mobs as high up as possible, perhaps with magma blocks with hopper minecarts underneath, light up the ocean down to just below the killing platform, with jack-o-lanterns, glowstone or lanterns perhaps and then afk about 123 blocks above it (as high as possible but still low enough so you are within 128 blocks of the whole killing platform.
I generally build this kind of farm up high in the air out to sea. My platform at Y 190 and the the drop distance depending on whether I want XP or loot above and then the spawn zones above that. This avoids need to light up the underground area. As long as you are over 24 blocks from the nearest spawn area and under 64 from the fartherest you should have plenty of mobs.
Recently, I've been putting a nether portal on the wait platform so I don't have to climb up there. Just hop into the nether, walk a few blocks, and pop out ready to go.
The dimensions I just cited for my typical bui;d means that above 64 blocks you will hit world ceiling. I suppose one could make a gigantic spawn platform and get over 64 blocks away in the X or Z direction but I can't think why anyone would want to