carbon

[brewmaster15]

Hi Fishmama,

Is it possible that AC left in place after "useful life" may become a favorable environment for secondary growth of undesirable bacteria and/or parasites? Hence, the conclusion that "It must be the carbon."?

At the point the carbon becomes "spent" and no longer capable of chemically removing things from the water, it really becomes nothing More than biological Filtration.. The moment you put it in the water , those same pores at which chemical filtration occur, are excellent places for beneficial bacteria to grow.....so basically it becomes an extension of your biofilter.

Is it useful? It depends on the application....Theres absolutley no doubt that it is excellent for removing things from The tank...but so is a good solid water change.. with added benefit of a wc removing possible parasites and nitrates...something Carbon does not do.,,Additionally the water change has the added benefit of replacing minerals to the water at a proper level.. and decreasing a tanks tendency to drift up in mineral content when the tank only gets topped off after water has evaporated.

Hth,
al

[Timbo]

and decreasing a tanks tendency to drift up in mineral content when the tank only gets topped off after water has evaporated.

an excellent point Al and one i'm sure some folks are not aware of. when water evaporates, only pure water is lost. no minerals, no pollutants, no salt ever leaves via evaporation; the concentration of these elements only goes up until a water change dillutes them (and assuming the change-water is relatively pure, also unlikely unless RO'd)

[fishmama]

Thanks Al!

Excellent info and answered my question...and then some!

Lisa

[crazie.eddie]

I like this thread, becuase I have referred it to several other forums. After doing more research, I found more information...

Con/Myth #4: Old carbon will leach organics back into the water (de-absorption)

This is true in industry, but not in our aquarium. Carbon is widely used in industrial settings to recycle precious metals. Industrial use of carbon involves the capturing of a specific substance at one pH extreme (below 4 or above 10) and then reclaiming the substance by converting to the other pH extreme. If a pH shift of this magnitude occurs in an aquarium, carbon leaching organics back into the water is the least of our worries.
http://www.marineland.com/science/ar...visActCarb.asp

Quoted from this article

De-adsorption

De-adsorption is another phenomenon that is over-stated in the rumor mills about activated carbon. Again, it is an incomplete statement that is commonly used to described the process. It goes, in one fashion or another, as: don't use carbon because once its adsorption sites are full it will release, or de-adsorb, all the stuff it has adsorbed releasing a large amount of pollutants back into the aquarium. The implication in this sentence that activated carbon works something like a capacitor such that once at its maximum adsorption capacity, it instantaneously discharges all the bad things it has adsorbed is wrong. Carbon does de-adsorb, in fact, that ability is exploited for recycling precious metals. However, in a controlled industrial process, the quick release of the target substance is accomplished by switching the pH of the water. The basic process is to capture the target substance at one pH extreme (very acidic or basic) and then reclaim the substance by switching to the other pH extreme. As stated earlier in this article, these pH values are outside the normal range of aquaria. De-adsorption is not a process to be worried about.

Quoted from this Marineland article

Basically carbon WILL leach (de-adsorb) if brought from an extreme pH to another. As mentioned, if it there was a de-adsorbtion process, then it should be a no concern, becuase the extreme pH shift should be more of a concern. In an industrial situation, this is feasible. In a home aquarium, not a problem at all.