rlcline76,
That's why I suggested the Google search - the material itself isn't on the web, but the article and book it is in are mentioned, and discussed. It's here on RC somewhere, already, but the search feature is so difficult to use, I couldn't find it, so I'll post it again:
This is an excerpt from the section of my book, "Advanced Marine Aquarium Techniques" that describes this issue. Now remember, just because I wrote it myself does not make it any less valid, this has material been fully reviewed and edited. Unlike here on RC, when you write a book or magazine article on a topic, there is somebody watching over your work to ensure accuracy<grin>.
Copyright 2006 TFH Publications
... Early on, carbon was implicated as a cause of HLLE but the mechanism proposed was that the carbon removed some compound that was needed by the fish, and its removal then precipitated the onset of the HLLE. In some of these recent public aquarium cases, the carbon in question was old, or used in a very small quantity so it was not conceivable that the carbon had substantially removed any compounds. The commonality here seems to be the production of carbon dust through mechanical abrasion inside the filter system. One theory is that the carbon dust enters the open lateral line pores, causing irritation and lesions. This would also explain why carbon-induced HLLE would not be commonly seen in typical reef aquaria; foam fractionators and filter feeding invertebrates are both well known for their ability to remove carbon fines from an aquarium’s water. It would also account for cases where some people use carbon in their aquariums with no apparent problem â€"œ there seems to be a huge variation between forms of carbon in terms of what types will instigate HLLE lesions and what types will not. Small-grained, dusty carbons seem to be the worst, while large granule or pellet forms seem to be less of a problem. It may turn out that further study will show that carbon derived from one carbon source over another may come into play.
In one case that demonstrates this syndrome very clearly, a pair of juvenile Australian lungfish were quarantined for over six weeks and then moved into an exhibit tank. They showed no signs of any problems. After a month or so, some driftwood decorations had caused yellowing of the water, so activated carbon was added to the power filter. The particles were small enough that they escaped the carbon container and were injected into the water. Within a few weeks, the lungfish developed unmistakable HLLE lesions. As the condition worsened, it was decided to remove the carbon from the filter and change all of the substrate (as it was contaminated with carbon dust). Within four weeks of removing the carbon, the HLLE lesions were seen to begin shrinking and within two months, the lesions were completely healed. Since these fish were actively growing, young fish and the lesions were noticed almost immediately, the problem was correctable. In aquariums where the fish are mature, the problem was not identified early enough, or where the carbon fines could not be 100% removed, it is unlikely that the aquarist will be able to resolve this problem.
While carbon dust in water may not be the sole cause of HLLE, it is most certainly one cause, one that the aquarist can take steps to avoid. At one public aquarium, once carbon use was curtailed, and all of the substrate was changed in problem aquariums, no new cases of HLLE have developed in the over 3000 fish in the collection for over three years.
Jay
