Thanks for the discussion. Yes, I've read through the many threads on HLLE and have seen some pretty wild stuff. However, in a hobby with so much lore and as an Engineer myself I tend to gravitate towards the scientific studies. I learned this lesson the hard way when I first started the hobby years ago with using garlic to treat ich and have never trusted the lore since
I think this is a case of too much of a good thing can be bad. Yes, I've been using activated carbon in all 4 of my reef tanks for years without incident, and I will continue to use it but with more caution. However, this study was pretty conclusive to me that activated carbon is one cause of HLLE. In my particular case, the most probable cause. I was using over 3x the recommended of dose to remove the Cupramine. Furthermore the type of carbon I was using was Lignite (the worst in the study). I'll be switching to BRS Premium ROX carbon, which is not lignite based and much lower dust. I have an email into their customer support to find out more about the source of this type of carbon. I was planning on making the switch already had some on hand; I was just using up my cheaper Marineland lignite figuring it didn't matter.
The study did look into the effects of diet. While they were unable to correlate the effects of diet to HLLE itself a combination of poor diet and carbon was definitely the worst outcome so it shouldn't be ruled out. I still speculate that this could be more of a longer term cause. I've ensured that all of my fish in QT have an excellent diet with a lot of variety:
1. PE Mysis 2x a day mixed with Ocean Nutrition flakes and pellets.
2. Sushi grade Nori every day (damn expensive)
3. Brocolli once a week
Some valid criticisms of this study IMHO:
1. Ethics aside, I would have liked to see a much larger sample size (i.e. more tanks and more fish).
2. While the study linked activated carbon to HLLE, it did nothing to explain the biological process and why they are linked.
3. There may be many causes of the disease, we just don't know. If there's more scientific literature out there feel free to link.
Here's some good discussion between Julian Sprung and the author (see the comments section):
http://www.advancedaquarist.com/blog/activated-carbon-affirmed-as-causative-agent-for-hlle-disease