When things (food, fish, shrimp, etc...) decay they make ammonia (REALLY REALLY toxic) first. then bacteria breaks into nitrite (REALLY toxic), then different bacteria break it into nitrate (toxic.) I'm tired right now, but i think plants use the nitrate.
there are a couple reasons not to move live sand. One is that there are different type of bacteria living in the different layers of sand. The different types depend on how much Oxygen (O2) they get. the de-nirtifiy'n one are on/near the bottom, b/c they don't get O2 down there. These are anaerobic bacteria. (W/O O2) if they get to where there is O2 they will die.
Also, some critters will die when they get "squished" from having too much sand on them. You know some critters will go under the sand .5" or 1". (I don't know what depth, but I know there is one) If they cross that threshold (what ever it is for the different critters) they won't be able to dig their self out...
or the ones that live in tunnels... one could easily plug their hole with 1/4" of sand on top and they wouldn't be able to get out...
I think it is mostly, b/c of the bacteria though...
Some people have had good luck moving live sand, but I didn't. If the sand isn't very "old" it would probably increase the chances that it won't nuke your tank. Also the sand in my tank was 3-3.5" deep. if one has like an inch, it probably wouldn't matter much... Just make sure your rock are one the glass and not the sand. otherwise it might all come down...
If one did need to move and wanted to try to make it work. one could have extra water and a extra tank. move everything in the extra tank (or one of the LARGE rubbermaid stock tubs) move the tank with the sand, then put water in it, try'n not to disturb the sand. then wait a day or something and test the water. one might be able to test the water the same day...
I have not tried that so, I don't know if it works, but that is what I would've done if I would've known that I might lose almost all my fish and make my huge leather sick (which slowly died and raised my NO3)the day/day after I bought them. (that doesn't make the missus happy!!!)
I hope i didn't confuse anyone, I'm tired so I might not have made a lot some scene, but hopefully enough
Stephen