This thread is an interesting conversation about different philosophies and terminology in reefkeeping. But coming back to carbon dosing I have tried to provide links and plenty of evidence for many of the points below:
1. Reef tanks have been kept for years without it, and it's not required to keep a healthy and happy tank. This is a large statement and can apply to fuges, stocking densities and so on.
2. Some view carbon dosing as a band-aid, others as just feeding the microfauna that is not present in our systems when compared to a reef. Chemically it is much simpler than the fish food most people add.
3. Carbon dosing is effective at reducing nitrates. See the above point, some view the nitrates as an indicator of poor husbandry, others see the low nitrates after dosing and the carbon is just another husbandry technique.
4. Carbon dosing's exact mechanism isn't that well known. It obviously increases microscopic life, but does not seem to increase water column levels of bacteria. The theory is that nitrates and phosphates or utilized and skimmed out, but I have not seen skimate analysis.
5. Carbon dosing appears to be quite safe. Scouring many forums there are only rare reports of serious problems.
6. Issues can include stripping the water of all nutrients, increased cyano, and burnt SPS tips with alk that is too high. Cloudy water also can occur, but does not seem to be harmful.
7. Liquid carbon dosing can be used to feed, or help feed, filter feeding organisms, such as feather dusters and clams, along with coral.
8. It can be very cheap to dose.
9. It is a chemical, but so is the salt mix we use. Chemically it is much simpler than the fish food most people add. If you really want to be a stickler about being natural there are marine yeasts that produce ethanol.
Bioethanol production by mangrove-derived marine yeast, Sacchromyces cerevisiae. In fact, it appears they are very good.
Interestingly I found this converstation about the "slime" some get when dosing too much. Post 82, apparently this surgeon took some samples to the pathology lab and there were few bacteria present in the samples.
What's Your Problem With Bio-Pellets? - Page 4 - Reef Central Online Community. I wouldn't be surprised if they were extracellular polysaccharides, but hopefully more research gets done with carbon dosing. I would like to see analysis of skimmer contents pre and post dosing along with microbial population changes. Of course that would be bacterial only around 16s DNA, but with a bit of research perhaps some of the bacteria consumers could be included eventually. The Dr was using eco-BAK, so perhaps that lends credit to the manufacturer claims that their product is different from other pellets. Of course I dose to feed the microfauna, so I want the carbon in the display!