Oh man! Sorry as well... Hope things turn around for you..

Yes, good luck indeed. I know how it feels, I can only imagine how amplified it would be in a tank of this stature.

I'm sure you've checked, and sorry if I've missed the info, but you've confirmed that you're not getting a NO3 reading? Elevated NO3 can depress your pH somewhat.

ubber build, what is the final cost if i may ask?

I got a NO3 reading of 19ppm a few days ago. My last water change seems to have reduced that to 14ppm. Phosphates are also slightly high, measuring 12ppm yesterday. Not perfect...but not the kind of levels that kill coral.

Sorry to hear about your troubles, I hope things turn around for you.

I apologize in advance for a difficult to read post....
 

It has been a very challenging month or two...but I think I can say that the tank is on the mend. For the past week or so, I do believe that I'm seeing improvement in the coral health/colour and polyp extension. Here is what I believe happened.

1) My lights bulbs were nearing the end of their life. They were almost 1 year old and were not putting out enough light anymore.
2) As a result of less light, calcification slowed down.
3) As the tank began to use less calcium/alk, my Ca reactor began to deliver too much Ca/Alk.
4) Too much activity in the Ca reactor drove my Alk too high and burned off many of the acro tips.
5) I changed my refugium to a 'fuge/frag tank and began lighting it on the same daylight cycle as the tank. Combined with the fact that it is winter and the doors/windows of the house are always closed, the overall pH of tank tended to be lower than normal. This makes it even more difficult for coral to calcify. Tank was never reaching pH of even 8.0 at peak.
6) I shut the Ca reactor down completely and fired up my Kalk reactor trying to drive up pH.
7) I increased water changes, carbon and phosphate removal trying to drive Nitrate and Phosphate levels down. They were slightly elevated, but I now doubt that these were the problem.
7) I replaced the light bulbs. I measured that my existing bulbs were putting out 25% less PAR than the new bulbs.
8) Coral immediately began to look better. I had not realized how much coral colour had gone away.
9) Kalk alone began to fall behind Ca/Alk demand. Calcification was happening again.
10) I began dosing baked, Baking Soda in order to keep up with increasing Alk demand and carefully restarted the Ca reactor. The baked, baking soda tends to drive the pH up, but I still only peak at 8.1.
11) I put an addition flourescent light on the fuge and returned to reverse lighting cycle on the refugium.

So..in the end I now believe that my ONLY problem was that my bulbs were old. Everything else was a spin off effect from there. At this point, I believe the corals are healing. Unfortunately, some have suffered such damage that it will probably take months to recover completely. I probably lost 2 or 3 corals completely.

That's an important observation made possible by the little PAR meter. I'm glad that the time/money/effort that went into its purchase has paid off for someone in a tangible way.

As Dr. Evil would say: "One miiiiiiiiiiiiiiiiiiiiiiiiiiiillion dollars!"

The bulbs were scheduled to change out regardless, but the PAR meter gave me some hard data concerning how bad they had become.

I gave up attempting to accurate measure the PAR at various tank depths. I simply measured the bulbs at surface level with the lights a set height above that. That's about 8" or so and I can easily measure a 25% difference between my old and new bulbs (same bulb type) At depth, this seemed to translate into about 1/2 the PAR, but these readings were pretty sketchy.

Yes...now to follow up with that device every now and then to find out how quickly the bulbs fall off. Clearly, my original plan of annual replacement isn't going to work. Maintenance cost just went up!

Glad to hear you figured it out Brad...I'm a regular visitor to your thread and enjoy this build a lot.