Skimmer, if you got one. Else you need bigger water changes.
When I do water changes, I do 40L to the smaller QT, and 60L to the larger QT.
My main system, can handle being overfilled with 40L. The sump can take that, providing you do not switch off the return pump while busy. So I overfill main system with 40L. Drain smaller QT of 40L. Refill smaller QT direct from main system with 40L.
Do basically the same for the larger system, but first only 40L, then another go on 20L.
It is a big job for me. For a 100L water change, I move 300L of salt water. Including the 100L RO water for the salt mix. Plus refilling the RO drum and my job is to move 500L water from one spot to the next... Luckily I do this normally on a Saturday afternoon and I can have a beer while doing that.