Testing the different carbon sources available on the market and others which one can purchase such as vinegar, vodka, sugar.......etc. would have to be completed under controlled experimental conditions to try and eliminate as many possible interferences as possible, such as number of fish, fish food used, GAC, GFO, mechanical filtration used, other supplements added....................etc.
Simply comparing one tank to another would not really offer much critical information with all the differences found between two tanks.
A big factor in how well these different carbon sources will work for a hobbyist, may very well depend on the species of bacteria, symbiotic algae in coral, regular micro-algae, cyanobacteria, dinoflagellates present in one's aquarium. For example research has demonstrated that certain dissolved organics can effect these micro-organisms differently depending on the bacterial species found in coral. In some cases, some dissolved organics will cause bacteria to grow in coral which produce poisons that eventually kill the coral, whereas under non-dosing conditions other species grow which are beneficial to coral. This aspect is very complicated. Little research has been completed in the area, but the future holds many promises. So to summarize this situation, one hobbyist's coral may not have the same bacteria or symbiotic algae that another hobbyist's coral will have, even with the same species.
The average water column found in a reef tank can contain 10's of thousands of different bacteria alone, not to mention the other microbes present. The type and amount of dissolved organic matter present on one tank is quite different then another tank due to what food, vitamins, amino acids, carbon sources, coral warfare chemicals............etc are added to a tank. The chemical interactions between all these different dissolved organics is mind boggling, much less the interactions of microbes with the organics present in a system.
In short, a reef aquarium is a very complicated system which we have no means to measure all these interactions going on and one can only base the amount and type of chemical dosage on our visual observations, which is not all that reliable. If we see negative results in our coral, there can be many factors that can cause this. Limiting the number of changes we make to a tank should therefore be reduced to the minimum while experimenting and ample time is needed to see the results.
The questions that scientists are trying to answer now:
How do these different carbon sources interact with coral at the cellular level?
What combinations of organics cause synergistic effects resulting in increased disease of coral?
How does temperature interact with the equation, since temperatures over 82 degrees can cause problems for some coral and not others?
How does lower pH result in disease in some coral and not others, especially when the pH drops below 8.0?
Why do some bacteria and symbiotic algae become dominate over other similar micro-organisms which result in chemicals produced that kill the coral?
How does increased levels of heavy metals kill or cause problems for coral? They know they do, but how does this work at the cellular level? Is it in the coral tissue or in the symbiotic algae or both? Some of the latest research indicates both in some coral and not others.
How do some known adverse conditions such as high heavy metal levels interplay with adding high levels of dissolved organics? Both situations cause problems for coral, but does the combinations of these situations increase problems synergistically?
The list goes on for unanswered questions.
