Rinsed mine with water change water...20 lbs at a time...poured it in with a small bucket and it settled in a few hours...Yes it will get syphoned up I use a small stainless screen in my syphon tube. Thing is the debris will lay on top of the sand and not be deep like gravel.
I have the same problem of my sand getting sucked up the syphon. I don't really care that im losing sand, but i cant dump it into my sink/toilet b/c it will settle in the bottom of the sumps or septic tank.. where ever it goes to... Next time i clean im going to rubberband a piece of nylon stocking to the end of my spyhon tube and see if that will catch it.
Someone told me buying a sphyhon with a longer uptake tube will also help but i havnt tried it yet
Use a small stick attached to the tube to stir the crap off the bottom and the syphon won't have to be so close as to suck up the sand. I have slots cut in my syphon head 3" up from the end...Gotta recharge the camera batts. but it looks something like this...