Advanced Aquarists Skimmer Article

I'm new to the hobby, and I came across this article the other day. I thought it was interesting. I just thought I'd post it up here and read some feedback and generate debate amongst reef veterans.

From what I understand from this, the skimmer only filters out hydrophobic organics...anyone know how you get the non hydrophobics out.. (i.e. the other 70% of TOC dissolved in the water) ??

Would I be wasting money buying the latest and greatest skimmer?

Advanced Aquarist's Online Magazine - Feature Article: Further Studies on Protein Skimmer Performance

 

I was always under this impression, that a skimmer only takes out organic compounds, not inorganic coumpounds like nitrate, metals, minerals etc. That's what water changes are for.

 

"Conclusions about relative skimmer performance based upon these measurements:
1.) All four skimmers removed both BSA (protein) and TOC (organic carbon) with similar rate constants; in short, "bubbles is bubbles", and there was no significant difference between these four skimmers in their intrinsic abilities to strip organics from saltwater.
2.) Only about 20 - 30% of the measurable TOC in reef tank water was removed by skimming, whereas almost all of the BSA was removed from saltwater by skimming."

later in the article.....

"One of the more surprising and important observations to emerge from the earlier skimmer studies was that the four original skimmers tested removed only 20 - 30% of the measurable TOC in the reef tank water examined; the remaining 70 - 80% of the TOC was not removed by skimming. Extension of these measurements to the three new skimmers tested in this study did not add much to the argument. The Reef Octopus' removal amount fell within this range, whereas the Bubble King and Royal Exclusiv skimmers appeared to remove incrementally more of the extant TOC, perhaps up to the mid-30% range. An explanation for this observation was offered in the January 2009 Advanced Aquarist article; in summary, skimmers can only remove what bubbles trap, and bubbles only trap molecules and/or particles (i.e., bacteria, diatoms, etc.) with some compelling thermodynamic reason to adhere to the bubble's surface. On the molecular level, this surface association is typically driven by the molecule/particle having a hydrophobic (= water hating) patch that can be buried in the bubble surface/interior. This arrangement avoids the energetically penalizing juxtaposition of hydrophobic surfaces with (hydrophilic) water, and so overall the system energy is lowered (a favorable occurrence). Some of the molecules/particles in aquarium water will meet this hydrophobic region criterion, and some will not. The ones that do not have a sufficiently large hydrophobic patch will not interact with bubbles, and hence will not be removed by skimming. From, the results of the experiments described here, it appears that only 20 - 35 % of the measurable TOC meets this hydrophobicity criterion (= [TOCl] defined earlier) whereas the remaining 65 - 80 % does not (= [TOCr] defined earlier). In essence, bubbles are a rather poor media for removal of organic nutrients from aquarium water compared to, for example, GAC. "

 

I will have to read through the article fully, but it is interesting. I would still however rather have the 30% removed then leave it in the tank. Thanks for posting it.

 

I have read both articles. Most manufacturers have been reluctant to submit for testing. Their claim is that bovine waste is not reef waste. Of course, the other reason may very well be that there is not a significant difference between bubble machines or different designs.

I don't understand why a standardized reef waste sample can't be formulated and used. Throw that in a new SW for a total concentration and test.

While 20-30% seems insignificant, skimming has been show to have great success at keeping a reef these days. In the past, turbulence was a desired effect and said to increase conact time. Now adays, there are many tweaks at reducing turbulence. Bubble plates and cones. The thinking now is that reducing turbulence helps remove more water loving DOCs to have a net lowering of total dissolved organics. The study shows a large percentage of DOCs remain, but many DOCs are not water hating molecules that are removed from skimming.

I do agree with the studies premise: that manufacturers claims are wildly unsubstantiated and a standardized test needs to be developed. It might indeed show no significant difference between designs. Even still... 20-30% still means that those that remove 30%, remove 50% more than those that remove 20%. That is a wide margin if indeed we can only achieve a 30% reduction of TOCs.

While the study may show no significant performance difference, there are still those that enjoy premium products. While build quality might not improve performance, it is still desirable. Also, pump quality is a huge factor when determining efficiency, noise, and reliability. Today, most of the cost of a skimmer goes towards quality pumps and those that wish to have them. Definitely interesting article though. If anything, it does give some peace of mind to those that are more budget minded in this hobby.