I just did that very thing with a 5yr old 90g into my new 55g. It worked very well for me. I had maybe a 2 to 3 day cycle. That was it. But I believe it is very important to try and keep everything submerged in its original water during shipping. I move mine in rubermaid tubs, cheap at Walmart. I had about 6 20 gal size tubs. It was an hour drive between the two locations and the items were in the tubs for over 8 hours, (plumbing problems). But also IMO use the original water from the tank you are moving the stuff from. Be sure to bring jugs to transport the water in. With a little care and finness it can be done very successfully. I had one small pollup rock show signs of dye off but that came back in a week and I attribute that to possible damage during relocation. I did a 10gal water change everyday for the first 3 days, the another in 3 days after that and then another a week after that. But initially use as close to 100% of the original water as possible. The items that lived thru the transfer was 1-4" finger leather, probubly close to 150 varios button pollups, 1 green brittle star, 1 sand shifting star, 1 feather duster, maybe 50 varios mushrooms, a few yellow polups, 25 some odd clean up crew, a large sea cucumber, and 2 colonys of star polups. Here is a photo taken about a week after I moved it. New things pop up everyday still.