SPS Dying Off - Please help me solve this mystery

[liudachris]

I don’t claim or even imagine that a higher pH or alkalinity is necessary to be successful at keeping corals, but every reef tank is different and there are a lot of different corals with different requirements. In this particular tank with no skimmer we can reason that oxygenation is most likely lower, if there is no macroalgae refugium helping add oxygen or possibly helping stabilize pH, the reported pH of 8.1 there’s probably a swing all the way down to 7.7 with the lights off. Oxygen doesn’t affect pH directly, but it affects the ability of the coral itself to function properly. Feeding the coral at this point could then actually reduce the ability of the coral to use the available oxygen. The rapid tissue necrosis and how he described it starting at the base and moving upwards to me also indicates the problem is low alkalinity made worse by a lower oxygen level. If someone experienced tissue necrosis from high alkalinity which is very, very rare in my experience, tips burning on Acros would be from excess carbonate, low bicarbonate and a pH out of range from 8.6 and higher. His temperature is not out of range, but also is not helping with the pH or oxygenation at around 82F. I bet there was no gravel vacuuming and so as the detritus builds up, so does acidification. I don’t know how to manually keep pH consistent at 8.1-8.2, but it’s super easy to stabilize it at 8.3-8.4 with higher dKH.
“Although the beneficial long-term effect of feeding on coral calcification is very clear (reviewed by Houlbrèque and Ferrier-Pagès 2009), the short-term effects can be the exact opposite (Al-Horani et al. 2007; Colombo-Pallotta et al. 2010). A possible explanation for this discrepancy is that impairment of calcification resulting from zooplankton feeding is caused by a reallocation of energy, for example to prey capture. By investing energy into prey capture, which requires muscle contraction and mucus secretion by polyps, corals may temporarily stop calcifying. In other words, corals may be unable to allocate sufficient oxygen and organic compounds to produce the required energy for calcification while they are actively feeding” https://reefs.com/magazine/aquarium...al-growth-implications-for-coral-aquaculture/
Some guy named Randy Holmes Farley, who is actually the older brother of both Larry Holmes and Chris Farley says to me me one time, he says, “
What is the Acceptable pH Range for Reef Aquaria?
The acceptable pH range for reef aquaria is an opinion rather than a clearly defined fact, and will certainly vary based on who is providing the opinion. This range may also be quite different from the "optimal" range. Justifying what is optimal, however, is much more problematic than that which is simply acceptable. As a goal, I'd suggest that the pH of natural seawater, about 8.2, is appropriate, but reef aquaria can clearly operate in a wider range of pH values. In my opinion, the pH range from 7.8 to 8.5 is an acceptable range for reef aquaria, with several caveats. These are:

• That the alkalinity is at least 2.5 meq/L, and preferably higher at the lower end of this pH range. This statement is based partly on the fact that many reef aquaria operate quite effectively in the pH 7.8 to 8.0 range, but that most of the best examples of these types of tanks incorporate calcium carbonate/carbon dioxide reactors that, while tending to lower the pH, keep the carbonate alkalinity fairly high (at or above 3 meq/L.). In this case, any problems associated with calcification at these lower pH valuesmay be offset by the higher alkalinity. Low pH primarily stresses calcifying organisms by making it harder for them to obtain sufficient carbonate to deposit skeletons. Raising the alkalinity mitigates this difficulty for reasons that are detailed later in this article.”

I do vacuum the detritus from the sand bed when I do water changes every 2-3 weeks. I've purposely not installed my skimmer yet because I thought that the roller was pulling too much out of the tank.