Once again, while trying to find what should have been a simple answer to a question about carbon, I ended up having gathered far too much information to not feel the need to compile it within one area and since there is a vast abundance of material already put together by others with some letters attached to their names, I will not attempt to repeat the same information and instead will just save you the time it took me to search through the many opinions and articles, and link to the ones that pertain to our hobby.

I will though list some information that I feel should at least be common knowledge by us as hobbyists with the above mentioned links following.

  CAUTION - Anytime new carbon is submerged into water, it will quickly drop the oxygen level. While this may not be an issue for larger tanks using commonly small amounts, a small tank can quickly become oxygen depleted almost instantly and will kill your fish. Of course this effect is all relative to the amount of new carbon used. If you are changing out a power filter pad that holds a few tablespoons of carbon, then you have nothing to worry about. But if you are changing out a carbon tube or cannister filter, I would first soak the new carbon in a container of aerated water (use an air stone) and let it sit for an hour or two before adding it to your system.

- Carbon use is one of a personal choice, if your system, such as mine, receives very frequent water changes, then carbon use may not be of much benefit . For those who prefer not to do large, frequent water changes, then running carbon will help to alleviate organic compounds building up. Carbon use will not hurt your tank, so by running it, do not feel that you are risking anything. 

- Carbon can temporarily raise ph levels as it will initially drop CO2 levels, this should not be a problem if your alkalinity levels are within range.

- You can not recharge carbon, soaking it in freshwater, or baking it in an oven will do nothing at all.

- Carbon will not remove trace elements, while it is possible, carbon can only do so under extreme pH levels, of which our aquariums will never see such extremes.

- It is very important to pick only high grade carbon for use. A good way to determine a high quality carbon is by its ash content. The lower the ash amount, the better.

- The only reliable method that I know of to determine when the carbon needs to be changed is to monitor the DOC levels of the aquarium on a frequent basis, when the DOC levels are seen to be on the rise, then it would indicate the need to change out the carbon. This would require the purchase of the appropriate probe and monitor. 

- A powder form will be much more effective than a larger granular/pellet form since it will provide much more surface area for adsorption. This is where I feel a Vortex diatom filter comes into its own.

 While I am a proponent of running an aquarium system as naturaly as possible, I fully understand that the needs and wants of other hobbyists systems may not allow running an aquarium without some additional help in providing biofiltration and organic byproduct removal. Even systems such as mine would most likely benefit from the use of carbon and I do not run it simply because it is not available to me here and instead, have to rely on massive water changes, something not everyone wants to do, nor can afford to do. As such, I strongly recommend, no matter what your aquarium is or how it is set up, that you consider installing what has been proven ( See this Article ) to be a highly effective method of ensuring your aquarium system is at its best.  I believe this additonal filtration method  if used, will make a difference on a good many aquariums. A special thanks to Stan Hauter of about.com for his efforts and research in this area.