[untamed]

Believe me, I feel your pain. My coral continues to kick the bucket one species at a time. Hard to kill a hammer coral, though.

I'm looking back at myself and realizing that the tank was doing it's best when it was new. Now, two-three years in, things are more difficult. So what has changed? I'm going hard after accumulations of things...That means vaccuuming sand beds and siphoning detritus out of places I couldn't reach before.

I'm scraping walls of the sump removing millions of tubeworms...trying to reset the system back to the way it was when I started it.

The only other variable that has changed for me is that the fish are now MUCH larger and produce significantly more waste than they used to. I don't quite know how to deal with that one, if it is related to the problems.

So...it sounds like we are dealing a similar problem, although you seem to be having a bit worse time than me. SOME of my coral seems to be doing OK. I don't think you will find your solution in measurable water parameters.