how much rock to cycle a new tank?

[iansfishy]

So Im starting my new 180, and have a couple tanks already. I have to switch everything slowly to the 180 ( only home one day a week) and was wondering how much live rock I can cycle the new tank with ( 20 lbs , 5 lbs ? ) Im putting about 10-20 lbs of sand in the system as well. I dont want to have to buy more rock when i already have 200 lbs. Also will removing that much sand from the established system cause any damage ( gases etc.) or putting lots of sand from the established system into the new system cause problems in the new system ( once some livestock is in). Basically I have a 6 inch sand bed in my refugium in when i move it to the other house I dont want any crap escaping and effecting livestock. Any help would be appreciated.