Thanks. It's been a wild ride.
I had some major learnings along the way and recently hit a major setback.
Here are the three biggest learnings:
1. My Kalk reactor works well except when I have to add kalk (once a month). I designed it to be simple and inexpensive but I forgot to make it easy to maintain. I didn't add a drain to the bottom, so I need to remove some water before adding more powder. Unfortunately, one time, I forgot to remove the output hose from the DT and caused thick kalk sludge to flow into the DT. This killed or burned a number of my favorite corals.
2. I went out of town and my monster skimmer went nuts. It exported 200gals over a week. In a 600gal tank, that removed all the water in my surge, aux sump and most of my main sump. I asked a buddy to check it out. I remotely turned off my skimmer and he was able to add 200g fresh RODI from my reservoir. We added as much salt as I had ~ 100g worth. I was running pretty low on salinity (experimenting) with 25ppm (it was going great, by the way). That dropped my salinity down to 15ppm for a week and most of my hard corals died. I could see the reading but I had an angry wife who wouldn't let my buddy back in to add more salt.
3. I use several float sensors and use a mix of the lever type and the ring type. Most are the lever type and they run to my Apex to control refill and surge. Unfortunately, this type of sensor can get caked with organics and calcium. And when I travel, that seems to be when they get stuck. I'm working on replacing them now, but it stopped my surge and refill from working. No life was lost but what a pain...
Also nature was working against me. First diatoms, GHA, then cyano and dinos! The dinos came at the same time I got hit with marine velvet and lost most of my fish. Unbelievable.
Some heartbreak and waste but I'm not discouraged. I'm letting everything settle and working on closing out all the root causes and corrective actions to get a more failure proof system.
My parameters are great now: 35ppm salinity, pH of 8.2, Alk 9dKH, Calc 500ppm, Mg 1500ppm, no phosphates, nitrates, ammonia or nitrites.
I'm getting coralline growth but my rocks and shells have turned green with endolithic algae. I think it's my light intensity or spectrum.
Overall- things are better and moving in the right direction.