Since water is the most important element, I put and emphasis on frequency and quality. By this, I vastly reduce algae and my tank stays crystal clean.
Source:
RODI only, I have a 250L, so I make 30L of RODI water for the week, 25L for the change, 5L for the daily top off which last the week as well. If TDS goes above 2ppm, or the colour has changed, whichever comes first, I change the DI Resin.
Turning RODI in Saltwater:
In a Brute Container, I add 25L of RODI and have a powerhead as a mixer. Two nights before the change, I mix in the salt and bring the mix to 1.025, as I have corals.
Every Saturday:
I take out 25 litres (10%) and replace with the newly made saltwater. I use all the saltwater in the container and then clean and dry the container for next use.
Been doing it this way for more than 25 years.
Everyone has a different way, frequency, some have not changed water in 6 months.
Depends on what you want to accomplish....