Just reading thru this interesting post and i think that you are missing one of the most important points in biology: all living animals need NPK. K has been totally forgotten from the equation by the aquarium hobby as a whole and you should try to supplement K and check the reaction of your corals as suggested in the attached article.
http://www.burgerszoo.eu/media/108815/chapter 16.pdf
Summary is that there is a large consumption of potassium in a reeftank and that is not properly measured (it is impossible with the currently available test kits to have a precise measurements as they all depend on dillution of 10x+ which grealty impact the precision of the results).
I would suggest that you add a good wallop of potassium supplement to your tank and check the results in terms of PE, colours and slow down/ improvement of the STN. The article suggests to add 50mg/l which i think is too much. Start with 1/10th of that.
Good luck!
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http://www.burgerszoo.eu/media/108815/chapter 16.pdf
Summary is that there is a large consumption of potassium in a reeftank and that is not properly measured (it is impossible with the currently available test kits to have a precise measurements as they all depend on dillution of 10x+ which grealty impact the precision of the results).
I would suggest that you add a good wallop of potassium supplement to your tank and check the results in terms of PE, colours and slow down/ improvement of the STN. The article suggests to add 50mg/l which i think is too much. Start with 1/10th of that.
Good luck!
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