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The protein skimmer
Commonly used in marine aquaria from the sixties of the last century when it belonged to the minimum equipment of a marine aquarium together with a UV lamp and a large biofilter. FDeGraaf1969)
My first seawater aquarium started in the seventies contained a countercurrent skimmer. Matricaria)
Skimmers where sometimes used in combination with ozone.
Is part of most if not all seawater aquariums. Is an essential part of the Berlin system and derivatives.
The main objective of a protein scavenger( skimmer) is to remove as much as possible organic matter from the water column so that it can not be mineralized.
Organic compounds usually refer to compounds that contain carbon and hydrogen. Often organic compounds contain nitrogen and phosphorus. HolmesFarley2006-08)
Many organisms, from fish and humans to bacteria, take up organic matter as food, as energy source, and secrete phosphorus and nitrogen surplus that is not used for cell retention and growth. The excreted organic material consists of carbon, nitrogen and phosphorus and other essentials and for the energy production is excreted as inorganic CO2, phosphate and ammonia which is subsequently converted to nitrate by bacterial biochemical processes.
Many metals, such as copper, are firmly connected to organic compounds in seawater. #4)
When metallo-organic compounds are skimmed, this will contribute to better water quality if there is an unwanted amount of it but may be problematic when the amount present falls below the limit needed for growth and live. HolmesFarley2006-08)
The term “organic compounds” contains everything from sugars, starch, protein, DNA and fats to fuel and gasoline, car tires, glue, plastic, plexiglass aquaria etc. For us very important are the harmful organic compounds and which are characterized by to accumulate in aquariums or are problematic in small quantities. Organic substances which, if not removed, are mineralized. Toxins derived from bacterial activities secreted by corals and from other organisms. Most compounds that colour the water yellow in a ZMAS. Many but not all of these organic compounds can be removed with a foamer.
Organic compounds are either hydrophobic or hydrophilic. They either hate water or love water. They dissolve well in water or dissolve completely not or partially in water. Hydrophilic molecules include water, salt, sugar, ethyl alcohol, ethylene glycol, glycerin, glucose, ammonia, most amino acids (e.g. glycine), some vitamins (B6, B12, Biotin, C, Niacin) and almost all inorganic compounds. Examples of hydrophobic molecules are methane (natural gas), oil, fat, cholesterol, fuel (e.g., hexane, butane), some vitamins (e.g., A, D, E, K). Among them are cases of doubts such as aspirin, phenols, cleaning alcohol (isopropanol) and acetone. Large organic molecules may be partially hydrophobic and the other part hydrophilic. Fatty acids, most proteins, soaps and detergents, and a wide range of biological molecules fall within this category. One can easily be skimmed off and others not, some compounds can be skimmed off sometimes and sometimes not.
In order to bind a bubble, at least part of the molecule must be hydrophobic. Compounds that are easy to dissolve can not be skimmed like salts, inorganic phosphate, carbonate etc.
Some organic ingredients, microbes, micro and phytoplankton, etc. can be carried by the foam and be excreted that way. FeldmanEnCo2009-1)
Significant benefits are associated with removing organic compounds and skimming is one of the best ways to do that. Other good ways are the use of activated carbon and ozone. HolmesFarley2006-08)
The past decade a lot of different types of polymers are developed with the capacity to absorb organic molecules, DOC, and which showed to have the potential to perform better as activated carbon. Some of these polymers are able to remove all types of organic compounds,hydrophobic and hydrophilic.(De Mille 2019)
When using a BADESS, the occurrence of mineralization is not a problem. The main purpose of a skimmer is no longer that important. The use of a foamer can be limited to removing the unwanted by-products of bacterial activity and for aeration of the water. To what extent these unwanted substances are removed, I do not know yet. It is important to know this to determine if the benefits still outweigh the disadvantages. There are other means to aerate.
Whence the name protein skimmer? The concentration of proteins found in natural seawater (as amino acids) is about 0.02ppm to 0.25ppm. This is 2-3% of the DOC (dissolved organic material) that can be found in an aquarium. Data published by Shimek from a survey of 23 hobbyists aquariums reporting protein concentrations of 0.00 + -0.00. They were not detectable. Other organic waste, primary and secondary amines, sugars, alcohol, fatty acids were detectable. Fats of 1.361 + - 0.94 ppm to 3.2ppm. Shimek2002).
We ask what a protein skimmer removes if it is not protein? And why the name if there are no proteins to be removed?
Dissolved Organic Compounds (DOC)!? This is where skimmers (I leave the prefix protein away) are in fact made for the removal of the by-products of the decomposition of biological material. FMarini2002).
The place where the protein skimmer is situated in the filtration system will determine the efficiency, especially when using biofilters. A flow as high as possible is desirable to prevent mineralization as much as possible, but excessive flow has no use. Escobal1996) The skimmer will be placed before the biofilters. Otherwise, nitrate production may be about + 15% higher. Also, a mechanical filter placed in front of the skimmer causes more nitrate to be produced.
When using BADES, the skimmer acts primarily as an aerator of the filtered water and for removing the products and by-products of bacterial activity and other substances that adversely affect water quality. Orthophosphoric acid is easily removed with a skimmer. Probst, Karl, Jürgen Lange, and Regina Brendel. Elsevier's Big Sea Aquarium Book. Amsterdam: Elsevier, 1976. Page 27 The occurrence of mineralization is no longer the main objective. The foamer can in this case after the bioreactor. A protein scavenger in the form of a bio-skimmer belongs to the possible equipment.
In biofilters, it was found that the solubility of mineral carbonate, calcium carbonate, is little or not affected by the grain thickness due to the rate at which the particles are coated with dissolved organic substances, by charged organic substances in solution. SHSpotte1979) Assuming that a skimmer can largely remove these organic substances, this obviously plays a major role in the decision making for the placement of the skimmer or the use of activated charcoal.
The use of a moving bed reactor may prevent the coating of particles.
Does a skimmer now do more harm than good or vice versa. And for a reef aquarium in particular? On this question, Ken Feldman and Kelly Maers try to find an answer. They compare different brands and types of skimmers. The research was published in the Advanced Aquarist Full IX, January 2010. FeldmanMaers2010)
Information about DOC (dissolved organic carbon), TOC and the influence on corals in marine aquariums by the hand of the same authors. http://www.advancedaquarist.com/2008/8/aafeature3 /. FeldmanMaers2008-08)
This is mainly about the removal of organic substances or TOC (Total Organic Carbonate). It is concluded that there is little difference between different types of skimmers in the removal of TOC. The way in which air bubbles are produced gives even upright results, airstone, venturi, needlewheel, downdraft, the result remains limited to the removal of 20% to max 35% of the measurable TOC. FeldmanMaers2010)
TOC can be subdivided into FeldmanMaers2010):
- TOC that is removed by a skimmer.
- TOC that will not be removed by a skimmer
- TOC consumed by microbes.
- TOC that is not consumed by microbes.
- TOC that is detrimental to tank residents directly or indirectly.
- TOC that is not harmful to tank residents directly or indirectly.
I would add: * TOC removed by activated carbon. * TOC that is not removed by activated charcoal.
There is no useful link between TOC values and ORP values. FeldmanMaers2010)
Ken Feldman wanted to know what's really going into the beaker of a skimmer and the conclusions are after thorough research: only a small portion of the foamed (solid + liquid) can be assigned to organic carbon (TOC); About 29%, and most of this material was insoluble in water, was not DOC (dissolved organic carbon). Most of the solids CaCO3, MgCO3 and SiO2 present, separate from the normal sea-water ions, were inorganic material. The origin of these substances can not be determined with certainty. Insofar as the solid is derived from microflora, some of the insoluble organic material is part of the microflora. This contains the nutrients P, N, and C taken from the water column through this microflora. FeldmanMaers2010)
The protein skimmer contributes to the removal of nutrients, such as phosphate and nitrate, to a lesser extent than expected.
This calls for research on the effect of a protein skimmer on the bacterial population in active aquariums and compare the results with a sample of the same water less subject to changes. The influence on the population of feed and the dosage of an organic carbon source. The purpose of the research is to confirm the organic carbon hypothesis. (Vodka dosage) Ken Feldman, Allison A. Place, Sanjay Joshi and Gary White are working together. FeldmanEnCo2011)
Bacterial growth is usually limited to the available amount of organic carbon. It appears that in a modern, constantly and heavily skimmed low-food aquarium, only + 1/10 of the bacterial population present on a natural reef is present, probably due to a lack of available organic carbon. FeldmanEnCo2011) In nature, the presence is low But the supply is inexhaustible.
The tests show that up to 39% of the total amount of bacteria present in the water column can be removed by the skimmer. FeldmanEnCo2011) This is less than expected.
Marine bacteria have a special need for sodium. Other elements needed for growth and propagation include carbon, nitrogen, phosphorus, oxygen, hydrogen, potassium, magnesium, calcium and iron. Many of the chemical compounds, organic carbon compounds, inorganic carbon compounds, amino acids, organic and inorganic nitrogen compounds, sulfur compounds, inorganic phosphate, etc. Marine bacteria can contain elements such as potassium, sulfur and store nitrate in their tissues at much higher levels as present in their environment. This results in the possibility that the water will be removed of these necessary elements to create deficiencies by bacteria export. FeldmanEnCo2011)
When organic carbon is dosed, only this element is provided, the rest must be extracted from the water column. A large part of cultured bio-load is not removed by a skimmer and remains in the aquarium and what is not consumed must be recycled and mineralized.
A more comprehensive overview of what is present in the water column and what is removed by a skimmer is shown in dit Article Roland L. Shimek Shimek decides that a skimmer associated with the export of organisms prevents most of the elements from accumulating in a normally fed aquarium. One is concerned about the heavy metals that remain. Shimek2002)
Feldman and Co conclude that mechanical filtration by foaming provides an effective way of exporting bacteria to a certain point. Some strains of bacteria are skimmable, others are not. Can skimming inadvertently cause severe evolutionary pressure on the bacterial population present in the water column in favor of the non-skimmable strains? FeldmanEnCo2011)
This statement asks for answers, the question of which strains are skimmed and which are not and the possible consequences. Should we question the use of a skimmer? And what about dosing organic carbon with the purpose of removing nutrients, nitrate and phosphate.?
Are PAO skimmable or not?
Delbeek and Sprung warns of drastic foaming of the water with skimmers, especially with downdraft skimmers. DelbeekSprung2005)
Feldman and Co estimate that only +30% of the measurable TOC is removed and that the remaining part of TOC can not be skimmed FeldmanMaers2010), also not at subsequent passes through the foamer.
Part of what is being foamed consists of non organic material, a large part of which is not undesirable.
If excessive foaming occurs, the ratio of unwanted and desired substances removed together from the water column will still decrease. These substances must be supplemented. Undesirable substances that do not become foamed accumulate.
The bottom line regarding the hypothesis of carbon dosing is clear; The fundamentals of this theory seem to be maintained in an experimental review. Dosage of carbon increases the bacterial population in the water column. And foaming removes bacteria with the stored food reserves. The scientific basics of this application are truth. FeldmanEnCo2011)
Supporters of an assimilation method (vodka) to assimilate nitrate and phosphate should take into account that only a portion of the cultivated bacteria are effectively removed by foaming. A part is attached and is not part of the water column, a part is not skimmable. Dosage of organic carbon will cause an accelerated imbalance in the presence of bacteria in the system, those who do not remain foamed remain behind. What types? I do not know (yet)!
Also, removed building materials must be replenished. When the aquarium is aggressively skimmed, this becomes a daily job
One assumes that corals have a symbiosis with surrounding bacteria, supply nutrients for their growth and using them as food. The lack of these bacteria could be one of the causes of bleaching. For more info see the Hologenome theory of evolution. More research has confirmed the importance of the coral holoboint and explains how.Anthias2019)
A quantitative evaluation of the protein skimmer. FeldmanEnCo2009)
Information on models and types of protein shavers is available in Dutch in 3 articles published in Hobbykwekers.nl by John de Lange and Adriaan Briene. They give a good picture of the various possibilities, including in combination with ozone use.
Deel 1; Deel 2; Deel 3
Between protein skimmers, there is a much greater variation in purchase price than variation in the ability to remove TOC. FeldmanMaers2010)
For the purchase of a protein skimmer,I have been guided by a publication of Pedro Escobal, Aquatic Systems Engineering: devices and how they function. Escobal1996) in which he explains how to calculate the maximum efficiency of a protein skimmer and how the air bubbles become made does not appear in the formula. The theory of Escobal is used as a guideline in an article by Frank Marini. FMarini2002)
Graber writes an article comparing skimmers with the requirements of Escobal: Skimmer design 101. SGraber2001-09)
In the article, the ordinary countercurrent skimmer is pushed forward as the best.
I have opted for a regular counterflow skimmer with airstone, with sufficient contact time. Like the skimmer I bought in 1974 but bigger.
Matricaria 2007
CMF De Haes 2017
De Mille 2019
~~DISCUSSION|Questions and remarks~~
The problem that arises when using a foamer is that the operation is difficult to judge. Is the use of a skimmer a good or a bad thing?
Holmes Farley makes a good attempt to explain how a protein skimmer works in an article in Reefkeeping: http://reefkeeping.com/issues/2006-08/ rhf / index.php. [(HolmesFarley2006-08>What is Skimming? By Randy Holmes-Farley - Reefkeeping.com [WWW Document], n.d. URL http://www.reefkeeping.com/issues/2006-08/rhf/index.php.
