I just moved a 125 to a 100. I went from CC
to 90 lbs of playsand and 60 lbs of LS
. I dont know that you would have a cycle with as much LR
that you have. Also use as much if not all of your old water and then add aged new SW
to make up the diff. I didnt have a cycle at all. I just checked today and all levels are stable.
Also if you add the water to the sand, I put down a big piece of plastic (new garbage bag) over the sand and gently poured the water over the plastic. Also you will need to weight the plastic down as you pour. My tank was only slightly cloudy for 1 day. Now its crystal clear...
Hope this helps. Take it slow and plan it out. It took me from 10 AM to 10 PM to get all of mine changed over...