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Two posts last year resulted in my interest in gaining a deeper understanding of how carbon dosing worked: @Miami Reef published the new organic carbon dosing schedule
www.reef2reef.com
and @Randy Holmes-Farley posted a question about why some aquarists find that dosing carbon takes a long time to see a nitrate reduction.
www.reef2reef.com
About two months ago I started an investigation of carbon dosing with two 2 liter model aquaria each containing 1.5 liters freshly collected aquarium water magnetically stirred. The acrylic aquaria were covered in aluminum foil. Each aquarium was dosed daily according to Miami Reef’s dosing schedule for vinegar. The concentration of the ethanol dose was adjusted to be equimolar with the acetic acid in vinegar (I titrated the vinegar to confirm its concentration), that is, I am dosing the same number of molecules of each organic carbon source. Also, phosphate concentration was adjusted during the experiment to the initial value when it fell below 0.1 ppm. Because I did not have enough stir plates at the time, there is no control for the aquarium water just stirring in the dark. Nitrate was measured with the Hanna high range nitrate test. Phosphate was measured with the Hanna low range test. Because of the size of the nitrate test standard deviation, comparing adjacent data points might be misleading and looking for trends of less than 5-7 data points is not a good idea. The plot of the nitrate concentrations for each organic carbon dosed is provided in the plot below. The dashed line gives the dose rate in mL/gallon. I became bored with not seeing much change in the nitrate concentration and cut short the duration of the 0.5 mL/gal dose.
Several things stand out in the plot. One is that not much happens at or below 0.5 mL/gallon. Maybe we should start dosing there. With respect to the data itself, nitrate concentration data from vinegar dosing aquarium seems bouncier than that for ethanol dosing. If this is not normal variation, then something is going on that is not explained by my simple notion of how carbon dosing works. Observation three is that ethanol dosing consumes a bit more nitrate. That may not come as a surprise. The next plot provides the phosphate consumption data. For clarity because the phosphate concentration was adjusted occasionally, the data is presented as the amount of phosphate consumed rather than the phosphate concentration in the aquaria.
The phosphate trend from vinegar dosing has an unexplained pause in phosphate consumption just after 10 days. The dip at day 19 could be a forgotten dose in both aquaria. What is interesting about these results and maybe just a coincidence is that phosphate consumption for ethanol dosing is higher than vinegar dosing by approximately the same amount as the amount oxygen needed to fully oxidize ethanol compared to acetic acid (1.5 x). I have more data analysis that I can trot out as interest and questions arise.
I have more experiments in the works to better understand carbon dosing. I am now using the low range nitrate test for better resolution and should be better prepared to sort out signal from the noise.
NEW Vodka and Vinegar Dosing Charts
The reasons I'm updating the Vinegar and Vodka dosing charts are two-fold: 1. The ramp was unnecessarily slow. There was no perceived benefit to such a tedious ramp, and it led to reefers quitting because they thought carbon dosing didn't work. 2. The ramp did not scale up correctly...
www.reef2reef.com
and @Randy Holmes-Farley posted a question about why some aquarists find that dosing carbon takes a long time to see a nitrate reduction.
Looking for thoughts on organic carbon dosing and nitrate
It is frequently claimed that it takes a long time (sometimes weeks) for organic carbon dosing to reduce nitrate. Do folks believe that is true, and if it is, why would it be true? Are most folks just starting to dose too slowly? Bacterial number increase is sometimes cited as a reason, but...
www.reef2reef.com
About two months ago I started an investigation of carbon dosing with two 2 liter model aquaria each containing 1.5 liters freshly collected aquarium water magnetically stirred. The acrylic aquaria were covered in aluminum foil. Each aquarium was dosed daily according to Miami Reef’s dosing schedule for vinegar. The concentration of the ethanol dose was adjusted to be equimolar with the acetic acid in vinegar (I titrated the vinegar to confirm its concentration), that is, I am dosing the same number of molecules of each organic carbon source. Also, phosphate concentration was adjusted during the experiment to the initial value when it fell below 0.1 ppm. Because I did not have enough stir plates at the time, there is no control for the aquarium water just stirring in the dark. Nitrate was measured with the Hanna high range nitrate test. Phosphate was measured with the Hanna low range test. Because of the size of the nitrate test standard deviation, comparing adjacent data points might be misleading and looking for trends of less than 5-7 data points is not a good idea. The plot of the nitrate concentrations for each organic carbon dosed is provided in the plot below. The dashed line gives the dose rate in mL/gallon. I became bored with not seeing much change in the nitrate concentration and cut short the duration of the 0.5 mL/gal dose.
Several things stand out in the plot. One is that not much happens at or below 0.5 mL/gallon. Maybe we should start dosing there. With respect to the data itself, nitrate concentration data from vinegar dosing aquarium seems bouncier than that for ethanol dosing. If this is not normal variation, then something is going on that is not explained by my simple notion of how carbon dosing works. Observation three is that ethanol dosing consumes a bit more nitrate. That may not come as a surprise. The next plot provides the phosphate consumption data. For clarity because the phosphate concentration was adjusted occasionally, the data is presented as the amount of phosphate consumed rather than the phosphate concentration in the aquaria.
The phosphate trend from vinegar dosing has an unexplained pause in phosphate consumption just after 10 days. The dip at day 19 could be a forgotten dose in both aquaria. What is interesting about these results and maybe just a coincidence is that phosphate consumption for ethanol dosing is higher than vinegar dosing by approximately the same amount as the amount oxygen needed to fully oxidize ethanol compared to acetic acid (1.5 x). I have more data analysis that I can trot out as interest and questions arise.
I have more experiments in the works to better understand carbon dosing. I am now using the low range nitrate test for better resolution and should be better prepared to sort out signal from the noise.
