if it's a fine grit I just skim the hose over the top. If it's real dirty I plunge the tip in and once the sand gets towards the top of the vacuum I just pinch off the hose until it falls back down. Heavier grits shouldn't have much of a problem.
I've found that it's easier to use just the hose and not even bother with the gravel tip thing on the end. Using the just the hose gives you a lot of suction power. Then take your fingers and stir up the sand then just vacuum up and things floating around. I'll post a link soon as I find it.
Edit: Found the link, it was originally posted by mike d.
I keep malaysian trumpet snails in my sand, they spend all day buldozing back and forward, turning the sand over like little ploughs, they keep it clean.
I keep malaysian trumpet snails in my sand, they spend all day buldozing back and forward, turning the sand over like little ploughs, they keep it clean.