I have added and have taken away sand...no biggie. Maybe go slow if at all worried. :biggrin:

We added a sand bed to our bb 210g reef 6 months after setting up after Irene and I agreed we hated the bb look as being very unnatural. No problems.

+whatever number we're at

New sand well rinsed should do nothing really. It's not alive at all and shouldn't really have anything on it to rot.

If you cycled sand in another tank and then moved it the sand itself would have die-off all over it from being moved and create problems I think.

whatever number we're at++;

I just recently replaced the sand bed in my tank. Scooped out all the old sand and dumped in new sand (carefully of course). I've done this in the past too without any issues (and will likely continue to replace my sand every couple of years or so) aside from a short lived diatom bloom.