I find there is not much difference vacuuming sand and gravel.
Because I do use pool filter sand, which is much more dense than play sand, or other lighter sands, and is meant to be backwashed yet sink back into position after washing, so although it gets partially pulled up a siphon tube, most just falls by gravity back to the tank floor.
But because detritus is not as easily worked in, the vacuum doesn't need to be jammed in as far to do the job of detritus removal.
Because I do use pool filter sand, which is much more dense than play sand, or other lighter sands, and is meant to be backwashed yet sink back into position after washing, so although it gets partially pulled up a siphon tube, most just falls by gravity back to the tank floor.
But because detritus is not as easily worked in, the vacuum doesn't need to be jammed in as far to do the job of detritus removal.
