I've just come through an almost identical episode as to what you've endured Dan. Same symptoms, same random deaths and STN/RTN. One thing that struck me reading through your thread is your switch to AF. I did the same.....and got the same results. I blamed everything BUT the AF products. I thought I had solved the issue numerous times but never thought it was the AF products. I eventually bit the bullet, stopped dosing all of the AF products, switched back to Tropic Marin salt, vodka and FM trace and within a month, the tank began to recover back to its former glory.
I know some people have success with AF but there are a few reefers now who have shown similar results as you and I. I therefore wonder if there have been bad batches/poor quality control? I doubt it is user error (I stuck rigidly to the instructions even to the point of under dosing). Or maybe its the AF products themselves that just don't suit some reefs. I'm hesitant to go with the latter as there are also success stories but it all seems a little too coincidental. I can only go from my own experiences with their products which wasn't at all what I'd hoped for and very nearly killed my reef and my passion for the hobby. AF is now off the shopping list as I firmly suspect this was the route cause of my issues.
Best wishes with the recovery, its heartbreaking when this happens.
Thank you Rich !!!
I have though so many times to blame the AF salt, but at the end , i do not have proof for that.
What I blame is my DECISION TO CHANGE WHAT IT WAS GOING WELL, with the aim to improve it more.
Today, when i go back to my pictures posted around December 2015, befire the change, I tell my self "what the hell you wanted to improve " if all looks so nice and colourful. BUT I DID IT !!! ..... changed the salt.
Was the AF salt ? Or was the change ?
I am now more convinced than ever that Was the Change !!!
I returned to my Reef Crystal's salt, and started to avoid doing anything to the tank. Just water change once a week and dosing Alk to keep it ~ 7-7.5
I do NOT have any idea of my Nitates or Phosp. levels, neither my Ca levels.
Why I will bother to know ?
If they are high you try to get them down, if they are low, you try to get them higher.....bottom line, we are changing the environment constantly. That didnt work in my hands and with all my travels.
I let the corals to decide their fate. The ones that find my conditions comfortable will survive. I kept those conditions stables (WC every weekend and 2 part dosing with b-ionic, the AF NP-pro dosing with the bacterias, and feeding always the same type and amount of fish food every other day ).
So far, under that policy, the tank has been recovering. And I am very happy with it.
Cheers
Daniel