Trouble in paradise...
The short story: I resumed adding vinegar to the kalk after a 5 week hiatus on Sept 21. On Sept 25th the corals start to STN. Sept 25-26 I accidentally roasted the corals with the light (I wasn't familiar with the auto-dimming feature of the ATI fixture). Between Spet 29-Oct 5 alkalinity creeps up to 9.75 dKH (7.5 dKH norm). 80% of the hard corals affected with STN, and 50% loss of the SPS.
If you want the full story, keep reading!
Sept 18th:
Cal 425 ppm (S)
Alk 7.9 dKH (H)
NO3 0.25 ppm (RS)
PO4 7 ppb, 0.21 ppm (H)
The rest of September I'm focusing on NO3 and PO4 trying to get nutrients up. I have been
pouring food into the tank trying to raise nutrients with no effect. I've been adding 4 spoons Coral Frenzy + 5 mL Fauna Marin Ultra Organic one day then the next I add 3 mL Pohl's Xtra + 1/4 tsp Oyster Feast + 5 mL AcroPower. Plus I've been feeding the fish 2-3 times per day as much as they will forcefully eat.
I took all those macro shots on Sept 25th (on pg 14), and during that time I noticed the fans in the ATI fixture weren't working and the fixture was auto-dimming, so I lay a room fan on it to keep it cool. Two days later many of the corals were quite bleached and I realize that the fixture must have been auto-dimming a lot for quite some time (maybe day one??). I turn off all the whites and have been running only the two blues at 80% ever since.
I noticed some burned/receding tips at the end of September and figure it was because I burned the corals with the suddenly brighter lighting, but I want to double check alkalinity so I check parameters.
Sept 29:
Cal 420
Alk 7.5
NO3 1 ppm (from NaNO3 dosing)
Oct 5th the burned tips are getting worse, so I check again and alk is 9.75, I check twice with two different kits. I stop the kalk doser. I had started adding vinegar back into the kalk (which makes it more saturated) which must be the cause of the spike, but I started the vinegar Sept 21 and the burned tips showed up around Sept 25th and the alk spike wasn't until after the 29th testing.
So I was scratching my head at this point. Was it the vinegar?? Works out to about 11 mL per day I was dosing into about 80 gallons volume. I was dosing kalk+vinegar from day one, and stopped the vinegar Aug 14th, then re-started Sept 21. The STN started 4 days after resuming the vinegar.
Oct 7th I check alk again and it's still at 9.75 despite removing the kalk doser, so the tank had
completely stopped using alk. I also note that pH is 7.4 without the kalk dosing, and I couldn't raise it by providing outside air. At this point I have about 25% of the SPS affected with burned tips.
Over Oct 7-9th I add 15 mL muriatic acid to the sump over 3 doses. This had no further affect on the pH, but did bring alk back down to 7.8. Currently, kalk doser has been offline since Oct 5th, and I haven't dosed
any alk in the whole month.
All the corals showing the burned tips around the end of Sept progressed into complete loss from the tips down. I pulled out about a dozen pieces. The STN has spread to more and more corals since - I have about 80% of the SPS affected by mid-October. My clam started gaping mid-October and perished 2 days later. I was worried that I may be looking at a total loss. My rainbow Trachy, anemone, and all softies were unaffected.
October 17th and 18th I did 17-gallon water changes, put a bag of carbon in, and promptly left the city for 10 days.
I came back to one more piece gone, but the rest look on the mend. Today I did another 17-gallon water change. My favorite pieces made it, but I ended up with about 50% loss all because of the perfect storm.