Why does my mob grinder not work in minecraft

I have built quite a big mob grinder/xp farm. It has five floors but when I'm at the bottom of the grinder 1 mob comes down after a minute. I broke the top of the spawner and saw that there were mobs in there but none were going to the water. Does anybody know why they are doing this.

This what the mob spawner looks like, i made it on xbox

That's what it looks like inside

That's what it looks like with no light. (gamma is on 100%)

Solution 1:

Typically mobs don't just run off ledges hanging in the air. They will however jump/be pushed into water at their level.

Judging by your pictures, there should also be more mobs - I would reckon that there are more caves and ravines to light up.

But, the important part is this: this design typically requires water streams at each level that funnels the mobs to the center. The mobs get pushed or jump into the water at their level and are funneled and dropped into the center. I have a similar setup, and this is what I have done, and it works adequately.

Please keep in mind the spawning rules as well: http://minecraft.gamepedia.com/Spawn. There are certain distances that must be observed or else mobs will despawn or not spawn at all.

Solution 2:

Mobs don't move at long ranges. At the distance of your first screen shot, it looks like the farm is > 32 meters, and at that distance mobs don't move. This kind of farm, you have to be very careful as to where you stand in order for it to work. The fact that you have mobs present indicates that you probably have the caves cleaned out "enough" but for massive spawn rates, I would recommend either cleaning out all the caves, or moving the spawner up quite a bit, (> 128) so that the only locations to spawn are in your facility.