Lando speaks the truth. Marine tanks should get smaller, less frequent water changes, to avoid upsetting the balance of things. Thus, you don't stock marine tanks as heavily as freshwater tanks.
I do a 5gallon water change about every 10-14 days on my 40 gallon tank. So barely a 10% change every two weeks. I have no cyano
, my fish are healthy, corals growing well, coralline spreading. Mostly I just have to keep up on alk
and calcium (since it's more of a reef setup)