Efficiency Project

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As a sub-project of my Fishsheets, I have begun gathering data from any aquarist who wants to submit his/her data. At this point, the primary goal of this data collection is to assess the efficiency of particular types of aquarium systems. Despite this relatively simple goal, the question of how efficiency should be measured has generated a lot of debate and discussion among new and experienced aquarists. As far as I can tell, most aquarists are divided into four ideological groups that define the efficiency of a freshwater aquarium system in the following ways:
  1. Overall Nitrate Production: Aquarists adhering to this position state that aquariums can be judged according to how much nitrate is produced by the aquarium system. This definition is very easy to test for, but it lacks any comparative value. For instance, lightly stocked aquariums generally have low overall nitrate levels even though almost all the the waste in the tank may be converted into nitrate. More densely stocked tanks may have high overall nitrate levels but very low waste-to-nitrate ratios. Consequently, overall nitrate production tends to only work when a tank is compared to itself. That is, if the overall nitrate levels of a particular tank drop (without increases in ammonia or nitrite), then that system has become more "efficient."
  2. Biomass Density vs. Overall Nitrate Production: This stance is identical to the previous except that the overall nitrate level is compared to the biomass of the fish (on a per-unit-of-volume basis). This method accounts for the problems seen when only the overall nitrate level is assessed in that stocking density is accounted for. At the same time, this definition of efficiency does not account for the effect of possible nitrate contamination in the water used to replace old water during partial water changes. Also, this definition fails to account for any nitrates or other nitrogenous compounds that may be intentionally added to the aquarium system.
  3. Biomass Density vs. Gross Daily Nitrate Rate: This definition is almost identical to the previous except that it requires a calculation to determine how much nitrate the aquarium is producing per day due to the nature of its operation. Particularly, this definition accounts for nitrate contamination in replacement water but does not account for nitrate contamination via fertilizers or other such additives. For aquarists that advocate this definition, it is taken for granted that any nitrogenous compound contamination that results because of the type of aquarium system (planted tanks needing fertilizers) should be counted against the aquarium system as part of its natural waste production.
  4. Biomass Density vs. Net Daily Nitrate Rate: Virtually identical to the previous definition of efficiency except that aquarists who favor this definition do not count any nitrate contamination against the system. In this view of efficiency, the potential harm of adding nitrogenous compounds is offset by the requirements of the system as a whole. Unfortunately, this definition is extremely hard to test for.
As can be surmised, I have opted out of using definitions One (1) or Four (4) due to either simplicity or extreme complexity. Choosing between the other two is much more difficult in that both are relatively easy to test and account for most basic conditions. However, as definition Three (3) does not call the system to account for tap water contamination, which is often beyond the aquarist's control, I have decided to operationalize efficiency as the ability of an aquarium system to keep biomass from being transfered to a daily nitrate production rate.
Of additional importance is how biomass will be defined and measured for my data collection. The definition of biomass that I will use will be the same as I use for my Fishsheets:
Biomass: "The impact of a biological entity or group of entities; a measure of the mass of something that produces a biological effect. Particularly, the impact of significant animals in an ecosystem." [Fish in the case of freshwater aquariums.]
As to biomass measurement, I will use a simplified IFU approximation that will assume that the average length is dynamically similar (after accounting for SAVI Theory) to average biomass. I grant that this method introduces a fundamental form of error into the system in that the biomass of each fish will not be addressed independently, yet I have done large-volume simulations comparing the process of accounting for each fish individually and the process of using an IFU approximation that revealed an average error bound of less than 25 percent. Consequently, my calculations will give the biomass a range of values oscillating 25 percent about the mean value (after accounting for feeding schedule) so as to nullify the likely error. To view the program that I used to calculate the large-volume error, download the attachment at the bottom of the page.
Also, my data collection survey will request some subjective data from the aquarist to compare how aquarists view their aquariums with the efficiency of their systems. Nonetheless, this subjective data will not be a part of the efficiency calculation--just auxiliary information that may be used to classify the results of this study. On the other hand, the aquarists' water change schedules will be used to account for how "clean" an aquarium system my be of its own accord. Also, the data regarding the water change schedule will help in determining the daily nitrate rate.
Lastly, the specific calculation used to assess how much of the biomass is being transfered to nitrate production will be as follows:
(IFUs/Gal.) X (Feeding Schedule Factor) X (TRANSFER FACTOR) = (Gross Nitrate per Day (ppm))
Solved for the transfer factor: TRANSFER FACTOR = (Gross Nitrate per Day) / ((IFUs/Gal.) X (Feeding Schedule Factor))
To participate in this study, click here.
Subpages (1): Efficiency Survey
MOA Fishkeeper,
Mar 27, 2010, 10:38 AM
MOA Fishkeeper,
Mar 21, 2010, 10:14 PM