Question on upgrading from 55 gallon to 75 gallon tank

When I went from 55 to a 90 I moved everything. Water, filters, heaters, substrate, decor, etc. I did not change filter media until a week after upgrade.I topped off the water difference over 3 days. Day 1 half of what was missing and then balance on day 3 so as not to shock the fish. I lost no fish doing it this way.
 
I went from 55 to 90 I borrowed buckets and also saved the water from the 55 (saved as much as I could) I reused the substrate, filters, and most of the water. After swapping tanks I simply put the fish in the 90. I did not top-off the tank all at once so I could avoid temperature fluctuations. Waited 3 days and did a partial, adding in more fresh water each time. I did this until tank was full. I lost no fish and never picked up an ammonia reading at all while maintaining my nitrates.
 
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