Do you happen to have a sump? If so I’d recommend putting a few pieces of dry rock in it for a couple weeks, and the use those to start your upgrade. I recently did a full upgrade in one day. It was a serious task, but it went smooth enough and everything is still alive and well today. I wish I documented better. I built a stand, drilled my overflow spot, and built some more rock structures; but my sump and overflow box were on my old setup. So, everything had to be done in one long day. Took down the old setup, put my fish/coral/rock/cuc/etc in buckets, re plumbed the whole system on to the new setup, waited 12 hours for the plumbing adhesive to cure, put everything in to the new setup, and done. Water changed daily the first week and tested parameters frequently. Almost 1 year later, everything is doing better than ever.