by oscar2001 on Tue Sep 25, 2001 8:32 am
THE CARBON THEORIES: There are several theories that the use of activated carbon in tanks may cause HLLE.
One version of this theory is that the carbon could be causing nutritional deficiencies by adsorbing vitamins or trace minerals either directly from the water, or by adsorbing molecules that the needed nutrients could then bind to. This theory, however, has several problems: There aren't any vitamins in tap water to begin with, and minerals like calcium, phosphorus, and iron should be available in large quantities in most prepared fish foods. Additionally, it is reported that fish rely on food for nutrients, trace and otherwise, making the presence of nutrients in the water irrelevant (4) although fish have been shown to be able to extract various minerals from the water (calcium, iron, zinc, etc.)
A second carbon theory is that some types of carbon may release toxins which cause HLLE. Perhaps a more specific variant of this theory is that some poorly manufactured carbons might release chemicals that cause stress to the fish. Another theory is that loose particles of carbon dust in the water have some caustic affect.
All carbon-related theories regarding the cause of HLLE suffer from one other significant shortcoming: HLLE can be found in tanks which have never had carbon of any sort used in them, yet is NOT found in many tanks using carbon. While it remains possible that carbon may be involved in some cases, there is no reason to believe it is a factor in most cases, if any. There is no sound evidence for a link, or even a logical specific theory--at best, the carbon-HLLE theories amount to a handful of individual cases where HLLE was seen in tanks using carbon, but appeared to improve after the carbon was removed. Since there is little to no information on what other steps where taken in the treatment of the HLLE, the association with carbon is rather suspect.
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