Upgrading tank, substrate questions

[NateL]

We are wanting to upgrade our tank and are wondering whats the best way to avoid a cycle. I have heard not to re-use the sand due to harmfull levels of chemicals that can be trapped under the surface. If we get new sand for the new tank, and seed it with some of the sand from our current tank and add all of our LR (100+ lbs) will we be seeing a cycle? We dont have room to run both tanks at the same time. Any advice or other suggestions would be greatly appreciated.

Thanks
Nate