Paul,
are you just doing WC? Running a refugium with mangroves helps get all the bad stuff out. You are correct on it depends on the type of tank.... my buddy wanted to go all natural and went with mangroves for years, the tank did okay but not flourishing. After a long debate and research he finally gave in and got one..now his tank is more stable and healthier corals.
Yes,water changes and nothing else,except live rock of course.
I do have a skimmer but I have yet to set anything up as far as a sump goes.
Truthfully,my tank has really flourished. I had a chalice grow about 3" or so in the last few months.
I just looked at my Duncans,and there are 4 new heads popping up.
My small Acans both have 2 new heads on them.
For some reason Zoas are not something I have had good luck with.
Truthfully,I was talking with my neighbor last night who also has a reef tank,and told him I don't even remember the last time I did any water tests.
He actually called me because some of his corals look crappy and wanted to know if I would foster them to see if the do any better in my tank.
I am in no way saying this method should be used or works for everyone,but so far for me it has worked out rather well.
I also have a couple of NPS and my tank gets fed daily.
Nitrates,I have no idea what they are