All of our major competitors pre-wash their carbons. We air vacuum our carbon before packaging it or using it in our filter cartridges. For this reason my carbon is much lighter than my competitors. It is also the reason it preforms so well! A good grade of dry, highly activated carbon, will be very active when it is first introduced to the aquarium water. It will, initially absorb a large amount of pollutants and toxic gases over a short period of time. After the initial burst of activity, the carbon will attract pollutants and toxic gases at a much slower pace until its absorbtion capacity has been exhausted. At this point the carbon is virtually useless! When carbon is being pre-washed, it is absorbing whatever chemicals, pollutants and gases that are contained in the wash water, at a very fast pace! After the carbon is pre-washed and then dried, its weight is increased by over 100%! This weight increase is added moisture and whatever contaminants that might have been absorbed from the wash water. Think of it as buying used carbon.