Best substrate that doesn't cause a chemistry flux?

[etgregoire]

I'm going to be moving in about 6 months, and I was thinking that might be a good time to do a substrate change that I have wanted. I know that moving a tank can be stressful for fish as it is, so what would be a good substrate that would not create massive swings in ph/kh/ammonia spikes, etc...

I won't be able to leave the tank set up to "re-cycle" without the fish in it. So something that leaches ammonia won't work for me.

I'm not very concerned about money because I have plenty of time to save up for it.

I currently have gravel, and am hoping for something finer that will allow for growing a carpet and perhaps darker in color as well.

Thinking Flourite Sand perhaps?

What do you think?