We may all want to read this article about skimmer efficiency. It is very well written, and one of the only, if not the only thorough scientific attempts to quantify skimmer function related to design, that I have read. I will quote from the 'Conclusions'...
Conclusions
Protein skimmers have become indispensable for many aquarists who strive to maintain the high water quality necessary to keep stony corals. This singular piece of equipment is typically the second largest expense after the tank itself, and as of this writing, there are at least 23 different skimmer vendors in operation. The advertising that accompanies these products often boasts of superlative performance, but no skimmer manufacturer has offered any quantitative support for their claims, in part because no useful metric for skimmer performance exists. In this article, we introduce two different measures for skimmer performance; (1) how fast the skimmer removes organic matter from salt water, and (2) how much of the existing organic material actually is removed. We demonstrate how these quantities can be obtained via experimental measurement and mathematical modeling on a model system consisting of Bovine Serum Albumin (BSA) in freshly prepared saltwater. In addition, we demonstrate that the trends among the numerical values obtained in the BSA model system also are observed with TOC removal from authentic aquarium (reef tank) water. The correlation between the BSA model system results and the TOC reef tank water results supports the hypothesis that BSA in saltwater can be used as an effective surrogate for TOC in aquarium water.
Four skimmers having four different reaction chamber volumes and representing four distinct types of bubble generation (needlewheel, venturi, airstone, and downdraft) were tested under the manufacturers' specified conditions. These tests revealed that there was no demonstrable difference between the Euroreef CS80 needlewheel skimmer, the Precision Marine ES100 venturi skimmer, the Precision Marine AP624 airstone skimmer, and the ETSS evolution 500 downdraft skimmer with respect to the rate constant for either TOC or BSA removal. Thus it is fair to conclude that, at least for the skimmers tested under the specified conditions, the individual manufacturers' claims of superior performance are without merit. Whether this conclusion can be extended to other skimmers remains to be seen.
Two operational parameters were examined; airflow rate and water flow rate. For the one skimmer tested at different airflow rates (Precision Marine AP624), the rate constant k for BSA removal did increase significantly as air velocity increased. The performance response upon varying water flow rate was not unequivocal. Using the Precision Marine AP624 airstone skimmer as a test system, increasing the water flow rate at first increased, and then decreased, the rate constant k. The basis for these divergent results has not yet been elucidated.
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.
Several critical questions that cannot yet be answered concern the generality of the conclusions drawn above. Can any skimmer beat the 30% organic removal level, or is that an intrinsic property of the TOC (cf. Fig. 1)? What are the effects of either gas flow rates or water flow rates that are far outside of the examined range, on k? Are there other unrecognized factors buried in the "k" term involved in determining skimmer performance? These questions can only be answered by examining more skimmers under a wider range of conditions.
From a different perspective, the methodology introduced in this article, in particular the BSA model system, presents a real opportunity for skimmer designers/manufacturers actually to optimize skimmer design/operational parameters in a deliberate and rational manner. Through these types of product development studies, skimmer manufacturers finally might be able to include descriptors in their advertising such as "best", "fastest" etc. that really mean something
Here is the link to the full article:
Conclusions
Protein skimmers have become indispensable for many aquarists who strive to maintain the high water quality necessary to keep stony corals. This singular piece of equipment is typically the second largest expense after the tank itself, and as of this writing, there are at least 23 different skimmer vendors in operation. The advertising that accompanies these products often boasts of superlative performance, but no skimmer manufacturer has offered any quantitative support for their claims, in part because no useful metric for skimmer performance exists. In this article, we introduce two different measures for skimmer performance; (1) how fast the skimmer removes organic matter from salt water, and (2) how much of the existing organic material actually is removed. We demonstrate how these quantities can be obtained via experimental measurement and mathematical modeling on a model system consisting of Bovine Serum Albumin (BSA) in freshly prepared saltwater. In addition, we demonstrate that the trends among the numerical values obtained in the BSA model system also are observed with TOC removal from authentic aquarium (reef tank) water. The correlation between the BSA model system results and the TOC reef tank water results supports the hypothesis that BSA in saltwater can be used as an effective surrogate for TOC in aquarium water.
Four skimmers having four different reaction chamber volumes and representing four distinct types of bubble generation (needlewheel, venturi, airstone, and downdraft) were tested under the manufacturers' specified conditions. These tests revealed that there was no demonstrable difference between the Euroreef CS80 needlewheel skimmer, the Precision Marine ES100 venturi skimmer, the Precision Marine AP624 airstone skimmer, and the ETSS evolution 500 downdraft skimmer with respect to the rate constant for either TOC or BSA removal. Thus it is fair to conclude that, at least for the skimmers tested under the specified conditions, the individual manufacturers' claims of superior performance are without merit. Whether this conclusion can be extended to other skimmers remains to be seen.
Two operational parameters were examined; airflow rate and water flow rate. For the one skimmer tested at different airflow rates (Precision Marine AP624), the rate constant k for BSA removal did increase significantly as air velocity increased. The performance response upon varying water flow rate was not unequivocal. Using the Precision Marine AP624 airstone skimmer as a test system, increasing the water flow rate at first increased, and then decreased, the rate constant k. The basis for these divergent results has not yet been elucidated.
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.
Several critical questions that cannot yet be answered concern the generality of the conclusions drawn above. Can any skimmer beat the 30% organic removal level, or is that an intrinsic property of the TOC (cf. Fig. 1)? What are the effects of either gas flow rates or water flow rates that are far outside of the examined range, on k? Are there other unrecognized factors buried in the "k" term involved in determining skimmer performance? These questions can only be answered by examining more skimmers under a wider range of conditions.
From a different perspective, the methodology introduced in this article, in particular the BSA model system, presents a real opportunity for skimmer designers/manufacturers actually to optimize skimmer design/operational parameters in a deliberate and rational manner. Through these types of product development studies, skimmer manufacturers finally might be able to include descriptors in their advertising such as "best", "fastest" etc. that really mean something
Here is the link to the full article:
