dartos, RE:
This carbon is supposedly only readily available to chemical labs, whether industrial or academic. They said that the carbon sold at an LFS or by the filter company would be no where near as refined.
There is an incredible number of variables that go into how well certain activated carbon will perform. Not just how it was processed, but its source turns out to be a huge factor. That is, the carbon made from Chinese coal is different from the carbon made from American coal is different made from tree bark is different from that made from coconut shells. As far as I know, there has been no real successful prediction as to excatly why these carbons act so differently. Yes, there are different trace materials, but the overwhelming majority is carbon. In short, the story about how effective carbon is is very long, and like many things in life, price does not really always indicate quality. Often the 'research' or 'scientific' carbon has been validated for a specific process or is bought because it has one specific property. The carbon in the LFSs, however, are from all different sources, and consequently have all different properties.
utahfish, RE:
you'll need carbon to start your bacteria colony
well, yes, but this does not come from activated carbon. I have fishless cycled tanks without carbon filtration. My guess is that CO2 provides most of the carbon at first, then dissolved organic carbons in the water are more than sufficient to provide the rest.
My first point about carbon is that unless you constantly change it out, it will rather quickly reach equilibrium saturation, and really be doing nothing at all. Even medium quality carbon will become saturated pretty quickly (the equilibrium is stongly in favor of carbon uptake). Even though the equilibrium is strongly favored to uptake, you have to throw it away after taking medications out of the water, because small (normally very very small) concentrations of the medications will come back out into your water. All this worrying about the carbon and if it is saturated and all that; especially since the benefits of carbon are few and debatable (20 something posts already!).
But, the most disturbing thing is that carbon will uptake dissolved organic compounds (DOCs) in the water. And those DOCs are performing a very valuable function! They are helping confer protection from metal toxicity. Metals readily bind to DOCs, and when the metals are bound to the organic molecule, they are not nearly as readily taken up by the fish. So, the DOCs from plants and fish that are being excreted are helping to pretoect them -- if you are using carbon you are taking away some of this protection!
Metal toxicity is often overlooked in water quality issues. For example, the toxic levels of copper and zinc in the water to be safe for fish are 0.02 ppm (Cu) and 0.1 ppm (Zn). By comparison, copper and zinc are not toxic to humans until in very high levels, and the regulations of the water companies are really based on taste. Normally, the water companies aim to be around 1.3 ppm Copper and 5.0 ppm Zinc. (All these numbers from Diana Walstad's
Ecology of the Planted Aquarium.) But, if you have these DOCs in the water, they can help neutralize heavy metals by binding with the metals.
Yes, your favorite water conditions probably helps detoxify heavy metals, but the DOCs in your tank are at the very least extra insurance. I wouldn't take away that insurance policy with activated carbons, again, especially since most of the benefits or carbon are minor or debatable.
