Sounds like you should get a water storage system.
Then you could use old de chlorinated/pre heated pre buffered if you like water and pump that into the tanks.
Gentlest on the fish and fastest.
And can do up to 100% change whenever you want.
Saying that its something on my wish list too.
All the best James
|My prob is if I turn anything off I get a senior moment and often forget to turn it back on.

So when setting up tanks I make sure all equipment is safe to run with at least 50% of the water out. Heaters and filter intakes. That way I can do small (anything under 50% I think of as small) water changes without worrying.