is the new aquarium going in the same place as your existing one? if not then then maybe try this. setup your new reef aquarium with your existing aquarium running as is. add rodi water to new aquarium about 2/3 full (mark it with tape), add salt + heater + powerhead for overnight. get the water parameter the same as your existing one. then add new substrate and a couple cups of existing substrate (i like 1.5" if it's very fine stuff, and if it is very fine stuff pre-rinse) and a few pieces of liverock, critters, hermits. sit for a couple of days, topoff water in both aquariums if necessary. test water parameter. transfer livestock over to new aquarium. transfer as needed water from existing aquarium to new. run filter + other equipment. make driploops, connect to GFCI outlet etc. I don't really like to keep old sudstrate so I would give them to new tanks as seeding material. I wrote this quick so correct if necessary.