On a roughly 1200glns system with a light load still I do 12% 150glns monthly water changes.
Its a simple turn valve to drain water and a switch to a pump to fill the system.
The more I load my tank eventually the more I will water change.

Water changes
 

In the beginning it was 10%/week of 550g and now it's it's about 6% of 700g every two weeks or 20 days.

A 1% difference in the amount of changed water has a large impact on my total running and upkeep costs. I'm hoping to eventually arrive to a 5% monthly change by the end of this year.

I have a 90 gallon reef with a 50 gallon sump, 90 has approx.70 gallons of actual water along with approx. 22gallons in the sump, been doing a 25% WC twice a month. Seems to be working ok.

10% per week.

total volume about 200g and last few months change ~50g every 2-3 weeks

10 gallons every week on a 140-150 ish system

im starting to think i should do it every two weeks...
due to unnecessary stress from going all out and diving into my tank *giggle*

or every second water change do the totally scrub everything , blow everything off , clean all the equipment.


clean freaks shouldn't own saltwater tanks im starting to think.

*i sometimes give my snails hair cuts*
i had one with a mohawk and one with pony tails kinda ..
when i had algae back in the day

I try to shoot for every two weeks

I change 40 gal every 2 weeks on my 120 With a 40 g sump.

I change 10 - 15 gal weekly on my 72 gal reef

15-20% bi-weekly = 40 to 50 gallons on 210 with 70 g sump