Just posting my hypothesis as to what is going on with this tank. A repost of my own comments on the "nuking this tank" thread.
"I just looked over your Micro-bacterial analysis again and noticed something. One of the extremely skewed bacteria that were found
Vibrionaceae is listed in a wikipedia to produce a toxin
tetrodotoxin and are extremely toxic ( not sure if to corals) in small amounts.
Also, a specific type of this bacteria that comes from this family is called
Vibrio anguillarum . It is listed to be "damaging to the economy of aquaculture sector and fishing industries". it might be because it kills things, not sure yet.
Wow Wow Wow I think I found it.
"The extent of the host range is seen with species such as V. mediterranei and V. coralliilyticus, which can infect zooxanthellae, the plant symbionts of coral. These species of Vibrio are thought to be a cause of coral bleaching."
Vibrionaceae - Wikipedia
en.wikipedia.org
This study has a lot of information about this specific strain of bacteria. I wish there was a microbiologist in this thread that could give us more information.
Temperature-Regulated Bleaching and Lysis of the Coral Pocillopora damicornis by the Novel Pathogen Vibrio coralliilyticus
But I'm also going through some of the other types of bacteria listed which your reef is
deficient in, to see if there are multiple issues regarding the bacteria (perhaps some limited amount of beneficial bacterias) which might be furthering the issues.
Also, if you saved some of that dead coral/ water it might be able to get tested for this specific strain and may give you the answer you're looking for.
I also realize that I might sound like a student conducting a science experiment here. I wanted to say that I do empathize with your situation (tons of money and time invested). And I hope that you really do get to the bottom of this.
The study concludes that the temperature of the surrounding Seawater in which the coral lives in is mostly responsible for determining the fate of the infection once the coral is exposed. They performed multiple tests of different species from this family and were able to reextract the isolated strains of bacteria from the deceased specimen. Every time a coral died they were able to isolate the bacteria in the tissue.
An excerpt from the conclusion of the study
"Several marine Vibrio species are pathogenic to invertebrates (
8,
16). The unusual feature of Vibrio bleaching of corals is that the target appears to be the intracellular zooxanthellae rather than the coral tissue. V. shiloi does not infect corals that lack algae (
2), and the bacterium produces anti-algal toxins that inhibit photosynthesis and lyse the algae (
3,
4)."
This brings up some interesting questions - like
Why is
your tank so full of this bacteria that is deadly to coral zooxanthellae
Is there a way to specifically target this strain of the bacteria
If you were to starve this tank of "food" for the bacteria by ceasing introduction of new coral for a significant time, could you starve out the bacteria similar to fallow periods for marine fish pests like Ich or velvet? "