How can you conclude it is inconsequential? In what context?
We don't how much of any particular organic compound is skimmed out, nor even know what specific organics are well removed and which are not (aside from speculating about the properties of specific organics).
Hi Randy; I was very interested in Feldmans articles. I respect him as I do you & hope I haven't misrepresented his finding.
The following is what I took from his research.
Feature Article: The Development of a Method for the Quantitative Evaluation of Protein Skimmer Performance
By Ken S. Feldman, Kelly M. Maers, Lauren F. Vernese, Elizabeth A. Huber, Matthew R. Test
Department of Chemistry, The Pennsylvania State University
Extract from Conclusions
Quote - All four skimmers were quite similar in the second performance figure-of-merit, the total amount of organics removed. The skimmers typically removed greater than 80% of the BSA.
In contrast, perhaps one of the more interesting observations to emerge from these studies is the fact that all four skimmers tested
removed only 20 - 30% of the total organics present in authentic reef tank water.
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Feature Article: Further Studies on Protein Skimmer Performance
By Ken S. Feldman, Kelly M. Maers
Department of Chemistry, The Pennsylvania State University,
Extract from the Conclusions
A perhaps more interesting observation to emerge from these
skimmer studies involves not the rate of TOC removal, but rather the amount of TOC removed.
None of the skimmers tested removed more than 35% of the extant TOC, leading to the conclusion
that bubbles are really not a very effective medium for organic nutrient removal.
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Feature Article: Bacterial Counts in Reef Aquarium Water: Baseline Values and Modulation by Carbon Dosing, Protein Skimming, and Granular Activated Carbon Filtration
By Ken S. Feldman, Allison A. Place, Sanjay Joshi, Gary White
Department of Chemistry, The Pennsylvania State University,
Our earlier research on the topic of carbon nutrient levels in marine aquaria (Feldman, 2008; Feldman, 2009; Feldman, 2010) has provided experimental documentation for four conclusions that impact on TOC management in our reef tanks:
1. Reef aquaria utilizing active filtration (GAC, skimming) maintain equilibrium TOC levels within the range found on healthy tropical reefs.
2. Protein skimming (i.e., bubbles)
is not very effective at removing TOC from aquarium water, depleting typical reef tank water of
only ~ 20 - 35% of the post-feeding TOC present.
3. G
ranulated Activated Carbon filtration is quite effective at stripping reef tank water of its TOC load, removing
60 - 85% of the TOC present.
4. And, quite intriguingly, the natural biological
filtration, which starts with
bacteria and other microbes, is remarkable in its capacity to remediate reef tank water of TOC, easily removing
50% or more of the post-feeding TOC increase in tank water.
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Feature Article: Elemental Analysis of Skimmate: What Does a Protein Skimmer Actually Remove from Aquarium Water?
By Ken S. Feldman:
Department of Chemistry, The Pennsylvania State University
Elemental Analysis Summary
An interesting and perhaps unanticipated observation is that only
34% of this solid skimmate material can be assigned to
"organic carbon", TOC. Thus, 2/3 of the solid, water-insoluble part of the skimmate is not TOC,
but rather inorganic material that may (or may not) have biogenic origins.
Skimmate Liquid Analysis
The bottom line, however, is that the skimmate liquid contains mostly the common inorganic ions that constitute the major ions in seawater.
Only a small amount of this material can be arguably assigned to dissolved organic carbon, DOC.
Further;
One of the surprising observations to emerge from the original skimmer performance studies is that only approximately 20 - 35% of the measurable TOC in aquarium water is removed by skimming.
That observation might now seem a little less surprising when viewed in the context of the skimmate component analysis. Thus, only ~ 29 % (25% from the solid + 4% from the liquid) of the skimmate removed by the H&S 200 skimmer from authentic reef tank water over the course of a week can be assigned to organic material.
So, skimming does not remove all that much of the TOC present in aquarium water, and the skimmate does not contain all that much TOC.
Conclusions
The chemical/elemental composition of skimmate generated by an H&S 200-1260 skimmer on a 175-gallon reef tank over the course of several days or a week had some surprises. Only a minor amount of the skimmate (solid + liquid) could be attributed to organic carbon (TOC); about 29%,
and most of that material was not water soluble, i.e., was not dissolved organic carbon. The majority of the recovered skimmate solid, apart from the commons ions of seawater, was CaCO3, MgCO3, and SiO2 - inorganic compounds! The origin of these species is not known with certainity, but a good case can be made that the SiO2 stems from the shells of diatoms. The CaCO3 might be derived from other planktonic microbes bearing calcium carbonate shells, or might come from calcium reactor effluent. To the extent that the solid skimmate consists of microflora, then some proportion of the insoluble organic material removed by skimming would then simply be the organic components (the "guts") of these microflora. These microflora do concentrate P, N, and C nutrients from the water column, and so their removal via skimming does constitute a means of nutrient export.
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Now, the above is the results from Feldmans indepth anaylsis, not mine!
but man, that tank is proof that "funky" works!
