Randy's vinegar dosing limit. I found it!
- Thread starter Randy Holmes-Farley
- Start date
Why does increasing the system’s volume not also increase the carbon dosing proportionally? Why is the maximum dose for a 25 gallon system 61 mL and a 1000 gallon system 124 mL? What am I missing?
Good catch. Maybe there is a mistake in that table. Hope that someone can explain.
The numbers are based on the vodka dosing chart, which are intended to be very conservative. The reasoning behind the lower proportions for larger tanks might be based on the cost or difficulty of water changes or other difficulties in dealing with a problem. You'd need to contact the authors to be sure, but I certainly would be more leery of larger doses in a larger and more expensive system that's much harder to handle. A few 30% water changes in a 29g system costs very little and the time and effort required is trivial. I have never managed a larger system, so I can't comment much. You could ask in the large tank forum.
Another possibility is that the author of the vodka dosing chart made a mistake. For now concentrate on the vinegar dosing chart which is derived from the vodka (ethanol) dosing chart.
If you convert mL of vinegar dosed to ppm acetic acid in the aquarium, the first two weeks for the 25 and 1000 gallon columns are the same, 0.43 and .87 ppm, respectively. This is as it should be. The incremental changes to the dose is where the author mistakenly added a constant increment across all columns (system sizes). That math error gives 33 ppm acetic acid for a 25 gallon system and 1.7 ppm acetic acid for a 1000 gallon system by week seventeen.
A minor point also to consider. Acetic acid and ethanol are not strictly interchangeable for dosing. While they both have two carbons, the energy derived from ethanol is higher. Acetic acid is a poorer energy source than ethanol and will require higher amounts than vodka. I have no idea at this point whether this fat would be discernible in a typical hobby aquarium, but it possibly addresses the nuisance organism growth difference, iffy as that topic is.
By surface area, that would be 33 ppm for 16 square feet of surface (approximately 25 gal) versus 1.7 ppm for 140 square feet of surface (approximately 1000 gal). In both cases I assumed a bare bottom.
I think it's quite possible that the chart is "wrong" for some value of wrong. As far as we can tell, it's very conservative, and much larger doses generally seem to be safe. That definitely could be even more true for the larger tanks.
I was guessing that the non-linear scaling was intentional, which isn't the same as useful or correct. It might not be intentional, though, and even if it is, I doubt that there's much data behind it. I don't doubt that we could find better numbers given a sufficient number of tanks for experiments.
You might be correct about it being a math error. That'd be funny. All the years I thought it was an excess of caution.
I agree that ethanol is a higher energy source per unit of carbon than vinegar. Vinegar basically is oxidized ethanol, after all. I don't know whether the the extra energy added causes more pests. A lot of the pests that seem to show up can use photosynthesis, as well, which muddies the issue of energy requirements somewhat.
In my reading on the subject on carbon dosing, there has been no mention of any special scaling rules. The dosing for systems greater than 25 gallons becomes progressively lower and lower, i.e., everyone has been underdosing if they followed the chart.
Now I assume the 25 gallon column is correct and the math error occurs in the rest of the columns. This assumption seems valid because the last week daily dosing rate of 33 ppm acetic acid is about 10 ppm carbon. That seems like enough to process a nitrogen import of about 1 ppm nitrogen per day. Something you might do with heavy feeding. I did this bunch of math in my head so treat it only as me being transparent about my reasoning.
No big deal though, right? The chart might not have been followed. Seems like everyone starts with a low dose of acetic acid or vodka and ramps up until they are satisfied or grow white slime, then they back off. I guess a potential issue is that folks might have stopped dosing prematurely because of the chart. We will have to let folks recall how their dosing regimen was impacted by the chart.
I just started dosing but I am thinking in terms of ppm acetic acid added and ramping up from 1 ppm per day to some multiple of the nitrogen imported via feeding.
It's the daily dose.
Who designed this dosing chart? It seems the vinegar chart was adapted by Randy and Cliff in their article in Reef Keeping. They derive their vinegar dosing chart from the earlier vodka dosing chart in a Reef Keeping article. In this earlier article, the authors said their information came from a thread on the subject and Jorg Kokott was a big contributor. Is Nathaniel Walton and Matt Bjornsen the original designers of the dosing chart?
My head hurts from reading old posts on the subject. In 2003-2004 Jorg Kokott was reporting that the Germans were attempting carbon dosing with vodka and said that he was going to write an article on the approach. I can't find that article. Later "œHeinz" started to post German posts to Jorg about the trouble they were having using information he was giving out. At one point "œHeinz" summarized the dosing regimen as "œnothing more than" starting with 1 mL vodka per 100 liters (I assume) which is about 25 gallons and increasing daily by 0.1 mL per 100 liters per day until the desired goal was achieved. "œHeinz" was like "œBelgian Anthias" in that he seemed to be warning everyone about the approach. I went to bed before going much beyond the middle of 2004.
Jonathan?
i have another answer. Jorg's article was rejected by Reef Keeping and its rejection caused quite a stir online, especially when Reef Keeping critiqued the article but wouldn't publish it. Now the search for the article got a bit more involved and interesting.
Interesting... But in the meantime, I think that we can agree that it should be pretty safe to dose 26ml daily (in 3ml intervals) to my 25 gallon system. Isn't it?
If Nitrate stays at 5+ in a couple of days and PO4 stays at 0.02 - 0.03ppm (or detectable), I plan to increase the daily dose of vinegar to 28 - 30ml.
If Nitrate stays at 5+ in a couple of days and PO4 stays at 0.02 - 0.03ppm (or detectable), I plan to increase the daily dose of vinegar to 28 - 30ml.
27ml would be in week 8, by the middle of the table.
At 27ml I'm still not seeing any noticeable change in look (corals, fish, etc., cyano, algae) and definitely no bloom. No change in Nitrate, Phosphate. MAYBE less green algae, which was already very much under control.
I am still uncertain what carbon dosing is actually doing and whether it works reliably from system to system.
Is the carbon feeding denitrifying bacteria to consume nitrates? Or is the carbon increasing bacterial consumption of ammonia and the existing denitrifying bacteria are able to "œcatch up" consuming the nitrate? Or both? And which systems get bacterial blooms before nitrate reduction occurs? And why?
I certainly agree that carbon dosing sometimes seems to fail. We could test the hypothesis about the direct consumption of ammonia by putting a bit of rock in a container with a skimmer, etc, and feeding it some nitrate. There's going to be little ammonia created if there's no food added. If the nitrate disappears, that could be due to denitrification or more direct consumption of nitrate, and less likely to be ammonia uptake. I'd need to think about this for a bit, though.
