How would that create an inefficiency per se.What cells are taking up ethanol and are they using it as a carbon source? . I'm not familiar with that part of the process. Doesn't ethanol oxidize to acetic acid in water via acetobacteria? Wouldn't acetic acid dosed slowly roughly equate to ehtanol in organic C content. How does all that impact the likelihood of a bacterial bloom.
thanks
I'll preface this with stating that I'm not a microbiologist and it's been a while since my last micro class. That said...
All bacteria can use ethanol (and acetic acid) as a carbon source. Ethanol needs to be converted into acetic acid (by NAD dependent enzymes, I can look up the exact enzymes if useful). This happens inside the bacteria. There are also acetobacteria who do a superb job of processing ethanol into acetic acid. They are actually used commercially to produce vinegar. This process happens inside the acetobacter and uses NAD-dependent dehydrogenase enymes.
I've not searched for it specifically, but I've never seen a mention of what specific bacteria are found in marine aquaria. It would be an interesting study for sure, but also difficult and of questionable utility (would be great to know, but if the bacteria populations are doing what we want them to, does it matter if we know?). So I'm not certain how much acetobacteria is (or isn't) in our tanks. The use of ethanol as a carbon source does not require there to be acetobacteria (but of course, doesn't exclude their presence either).
Ethanol needs to be converted into acetic acid inside the bacteria. Whether that is done by nitrifying / denitrifying bacteria or acetobacteria, both ethanol and acetic acid must be internalized. Active transport of acetic acid helps more AcOH (compared to EtOH) get into bacteria.
So... Why do I think ethanol is a "weaker" source of carbon than acetic acid on a 1:1 molecule basis? Because a) active transport of acetic acid and b) no conversion goes to 100%. Not all ethanol will be converted into acetic acid. Some ethanol will azeotrope with water and leave the tank altogether. That won't happen with acetic acid under normal tank conditions. I wouldn't claim one source is "better" than the other. Even if acetic acid is "stronger" it has pH issues that can be undesirable (but yes, easy to mitigate). I haven't been in the hobby that long, but I personally like the ethanol-acetic acid mix.
Bacterial bloom: I've observed that when I increase carbon dosing by a good amount, I get a bacteria bloom. This makes sense as you are giving the bacteria more "food". When you consider that NOPOX is mostly ethanol (and if you buy my arguments that ethanol is a "weaker" carbon source than acetic acid, I would expect a bacteria bloom going from a straight conversion (per mole carbon source) of NOPOX to vinegar only. Although my concerns seem to be overblown, marty did report a bloom going from NOPOX to 4x volume of acetic acid which is consistent with everything above.
