to siphon the gravel bed.

[dirtyreefer]

I would vacuum it as much as you can because your sand bed eventually becomes a nitrate trap. A cleanup crew won't get rid of your nitrates, they will just breakdown the uneaten food or waste before it becomes ammonia, and won't erradicate the nitrate.

There are people that swear by deep sand beds (DSB), but I have heard many people move to shallow to no sand beds. There are also alot of people that testify that a tank may experience a sudden wipout syndrome which is believed to be attributed to a deep sand bed.