Purhaps I can shed (no pun intended) a but of light on it. Biological filtration in LR and sand as we know is performed by bacteria reducing elements. The problem is that biochemical reduction is a very slow and not to effecient a method, vast numbers of baterial populations are required to perform the task, something we can not achieve in our tanks. According to the number put out reduction studies and supported by the perponents of sand systems (dr.R) they can only provide filtration for a very small bioload. I believe the conclusion was 2 to 3 small fish in a 100 gallon tank with a 6 inch bed.
With the bioloads that the mojority of us have in our tanks and the feedings we do, the result is a slow loosing battle, where the input of elements far exceeds the output. LR unlike sand systems does have an advantage, Because of it shape (no botton and side to constrain it) and through bacterial action (creation of enzymes, blooms, die offs and so on) and gravity, LR will shed its end products and detritus.
With the concept of cooking your LR is not so much that it is now in the dark, what it truely is, is that we are now stopping all input of nutrient/elements. This is basically allowing the bacteria to catch up and turning the table on the input/output of food to it. When doing this procedure you are not removing any of the so called beauty of any specimens nor are you turning the rock into base rock, actually you are returning the rock to more of a functioning peice of filtration and stopping it from being skewed into eurthropic and thus becoming a nutrient producer.
The method is not done in the aquarium either, normally the person takes out a peice or two and cooks them in a seperate container while the tank continues as normal. Personally I lack the patcience for this procedure and just remove a rock, place it in a pot of boiling fresh water and allow vapor transmission to remove all nutrients and lifeforms (yes yes I know what an evil man) once done I put the LR back into the tank. Yes all the life with in it is dead and I have lost filtraion from that particular rock, but I have also introduced a peice of LR that is wide open for occupancy by bacteria with out compitition or saturated with nutrients for bacteria and all other life forms, also the surface is now perfect as a seed surface for corraline algae, dusters and so on that do not have to compete for a spot to grow on with others. Again this is something that should only be done when all other methods have been exhuasted.
MIke