[sslak]

Totally disagree with Playa-1, but I think he misunderstood...or I do. You plan on adding all 120 lbs of dry right away with the 20 lbs of live right? You should. If you're talking about cycling with the 20lbs of live and adding 120 lbs of dry after the cycle...then I think you should wait until you have the dry rock before trying to cycle.

I think your tank will cycle just fine with what you describe. The good thing is you have some established live rock. This contains all the life you want in your new tank.

The only restriction is time...you need to wait for the life on that 20 lbs of rock to reproduce and populate the other 120 lbs. Your "bio load" will not be that of a 120g tank for quite a long time (weeks/months), so wait for the cycle, stock slowly and you will be fine!

The more live rock you add, the faster the cycle "should" be, but there are no absolutes.