hopefully this isn't too off-topic.....I still like my kalk reactor! (there!)
Water chemistry and nutrient levels are important to keep monitored with every tank and dosed tanks are no exception - however do keep in mind that for the filter feeder and microbial food chain benefits are use far less carbon that one would for lowering nutrients.
Very true and important to say! 
This is not a "carbon is evil" discussion, folks.
Every shred of algae and coral in our tanks is constantly dosing carbon into it and encouraging very specific bacterial communities.
So we're only figuring out our impact to the carbon cycle and how we might be obstructing or interfering with it and maybe how it stays balanced on its own. We're not demonizing anything except doomed tanks.
I've gone long periods dosing my own tank with vinegar, but only into the reservoir for my kalk reactor to boost its output. Carbon is neither evil nor useless.
However,
the effects of carbon dosing are poorly understood in the hobby. Witness the mystery side-effects and number of folks who use it vs phosphates.*
Regardless, the side-effects for us appear to be just as those described in the article I linked earlier for wild ecosystems with elevated carbon levels:
- Healthy = non-elevated C levels = a slant toward phytoplankton
- Unhealthy = elevated C levels = a slant toward bacteria
.....so we know at least some of the effects of "high carbon" when we see it. Usually only when it's too late and the dominant green algae have already died off and been replaced.
The end result is often a tank dominated by bad (literally harmful...not merely ugly) algae – not a tank with no algae. (Those only happen in pictures!)
Dino outbreaks are probably the "most popular" negative end result in the hobby, but not likely the only one as I also suspect a role for elevated carbon in "burnt tips". Need more cases to look at in detail in order to rule out (e.g.) GFO and nutrient starvation, but there seem to be
no cases of burt tips that are associated with a tanks that allow "natural" carbon levels and "natural" P and N levels.
If so many folks weren't starving their tanks from Day 1 out of fear of algae, we wouldn't have near the numbers of "carbon problem tanks" that we do today. Old school methods were (are!) better in this scenario.
Fear of algae drives a lot of negative behaviors.
No nutrient spike (or crash) = No bloom = No worry
Easy to put in an equation, but it means (in a nutshell) going slow so. I think that's the core of why it remains unpopular as a strategy.
-Matt
* To complicate matters, we have no way to assess carbon levels in our tanks the way they do in journal articles, so I can't say what "elevated" means to us with any precision. I think alkalinity is our only clue, but it's not clear if or how alkalinity, or alkalinity usage, is impacted by organic C dosing. (I think I've seen it argued that one doesn't impact the other, but I have trouble accepting this in a system that has producers of carbonic anhydrase converting back and forth.....there is a carbon cycle and this is a part of how it works.)
)
