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Author:Richard Harker
In recent years the spirited and often contentious debate over reef lighting has been joined by an eually spirited and contentious debate over protein skimming. The calm, agreeable discussions of the past about protein skimmers have been replaced by endless noisy debates over which protein skimmer is best. The fire storm was ignited by the introduction of the downdraft protein skimmer, a design quite different from previous protein skimmer approaches. The appearance of the first downdraft designs spawned a succession of protein skimmer introductions resembling an escalating cold war arms race. And, like a weapons arms race, each new entrant into the race was more powerful (and expensive) than anything before it. Early protein skimmers relied on bubbles generated with the use of air pumps feeding airstones. Later, Venturi driven protein skimmers joined air pump-driven skimmers, and the two approaches remained the primary protein skimming methods for nearly a decade. The suddenly changed in late 1994 with the introduction of the downdraft protein skimmer from E.T.S., designed and produced by Gary Loehr (Schiemer 1994). The downdraft skimmer uses a variation of the venturi principle to generate air bubbles. A large pump forces water through a narrowed opening at the top of a long tube. The "injector" draws air into the tube as the water stream expands exiting the injector. The air is than mixed with water as it flows over bioballs filling the tube.
The Most significant difference between traditional venturi skimmers and downdraft skimmers is the amount of air a downdraft skimmer mixes with water. The volume of air drawn into the skimmer is greater with a downdraft skimmer than a traditional venturi skimmer. There are, however, operationallimitations to a downdraft protein skimmer. The unit takes a very large pump to operate properly. A standard 5-foot tall downdraft requires a pump capable of delivering up tp 1500 gallons per hour against significant backpressure (because of the injector). Pumps capable of moving this much water are expensive to purchase and they consume a great deal of power. The volume of air mixed with the water is deterined by the water pump, so there is no convenient means to independently control air flow. In contrast, the traditional counter current, airstone-driven protein skimmer requires a less-expensive pump and can often share the water pump used to return water to the tank form a sump. Rather than create air bubbles with an expensive water pump, the bubbles are created with a much less expensive air pump and airstones. The volume of air flowing into the skimmer can be independently adjusted from the rate of water flowing through the skimmer, allowing the hobbyist a great deal of control over the ratio of the two. As will be shown below , control over this ratio is very important for the efficient operation of a protei skimmer.
The author of a review of the first downdraft skimmer(Schiemer 1994) made several observations on the relative performance of airstone-driven,venturi and downdraft skimmers. Without exception he noted that the downdraft skimmer "shut down" the other skimmers, leaving them apparently with nothing to skim. The review and gushing reports form early purchasers of the skimmer immediately caught the attention of the hobby. The mystical lore grew until it became one of the hobby's unchallenged "givens" that downdraft protein skimmers were far superior to older designs. Few have questioned this notion since and the debate has turned to whether newer downdraft skimmer designs, such as the HSA protein skimmer from Marine Technical Concepts, are superior to the E.T.S. downdraft skimmer. As with many technological innovations in reefkeeping, those who raise questions about the claimed superiority of new designs are often dismissed. This is unfortunate because if the critical issues in reef lighting are only dimly understood, the debate over protein skimming is truly in the dark.
Little int he hobbyist literature has addressed the issue of protein skimming from a scientific perspective. The debate has not been based on research or even a review of the long trail of scientific data on protein skimming. Instead, it has been based on questionable speculationand fuzzy thinking fueled by ignorance of the principles of protein skimming. While many aspects of reefkeeping are poorly understood, protein skimming stands out as one of the most confused and frustrating critical issues in reefkeeping today. What follows is an effort to examine the issue of protein skimmign form a scientific perspecitve using nearly a century of research on the subject. As I hope to demonstrate, the basic principles behind protein skimming raise questions about this escalating protei skimmer arms race. In my opinion, there is evidence that many hobbyists would be better served by considering the traditional counter-current protein skimmer rather than jumping on the downdraft bandwagon.
FOAM FRACTIONATION
Reading through the hobby literature, one would think protein skimming was invented in Europe in the early 1980s and migrated to the U.S. in the early '80s. It might surprise most reader to know that foam fractionation was first described nearly 100 years ago(Lush 1976). Foam fractionation is the formal term for the process the hobby calls protein skimming. The first "modern" protein skimmer was described in Nature in 1937. It was a device that would look at home hung on the back of today's reef tank (Schutz 1937). By the 1940s, scientists were actively researching the use of foam fractionation as a method to separate protein from solution (Schutz 1945), and by the 1970s researchers had a clear understanding of the principles and methods behind foam fraction. Most of the hundreds of scientific articles and books written about foam fractionation predate the first downdraft skimmers. However, the physics and chemistry behind protein skimming are no different todayh than they were the day the first head of foam was created in 1899. Even the earliest scientific literature can be of great value in sorting out the claims and counter claims of protein skimmer advocates.
Briefly stated, foam fractionation is "the selective adsorption of one or more solutes on the surface of gas bubbles that rise through the solution. These bubbles then form a foam atop the main body of liquid. This foam is relatively rich in adsorbed material and so when it is recovered overhead a partial separation of components results" (Lemlich 1968) . Note that there are two phase to protein skimming. The first phase is liquid phase in which the air bubbles are generated. The bubbles rise through the water, and as they journey upward they come in contact with surface-active proteins. Proteins make up a large part of surfactants- the molecules adsorbed by air bubbles. However, the proportion of proteins that are surface active and therefore can be removed through protein skimming represents only 11 percent of the proteins found in aquaculture systems (Chen 1991). This points to the need to use other methods of chemical filtration, such as activated carbon, in addition to protein skimming (Harker 1998). The second phase of protein skimming is the air phase. When the protein-laden bubbles reach the surface of the water, they collect as a layer of foam. This foam is then "skimmed" or collected, which removes the proteins and other surfaceactive molecules. Debates over protein skimming tend to focus on the endproduct of the second phase, the foam. The contention is that the mark of a good protein skimmer is a darkcolored, thick foam. I n my opinion, foam is not necessarily the best indicator of skimmer effectiveness, nor is dark foam necessarily richer in dissolved organics than thin foam.
I believe the liquid phase is more critical. Protein molecules are large and require a lengthy contact time with air bubbles before they attach themselves. A downdraft skimmer can generate a great deal of foam by virtue of the violent way it mixes water and air, but the large volume of foam created does not necessarily prove that proteins have been removed. Smaller molecules that are more readily adsorbed onto bubbles may be the only thing that a powerful downdraft is removing. Furthermore, the greater the volume of foam, the lower the concentration of proteins in it (Ahmad 1975). If efficient removal of protein is the goal, large amounts of foam may not serve as a useful indicator of effectiveness. Contact of residence time-the length of time bubbles remain in the water to attact protein molecules- may be a more important measure of pretein skimmer efficiency. Prokop and Tanner (1993) write, "The slow time for equilibrium is due to relactively low diffusivities of proteins, as they are quite large molecules." Schnepf and Gaden (1959) add, "Since diffusion rates in dilute protein solutions are low, the contact time between a rising bubble and the bulk liquid will be extremely important in determining the amount of surface active agent which can reach the surface." Research suggests that a contact time of up to two minutes is necessary for macromolecules like protein removal rates continue to increase up to a contact time in a downdraft skimmer is very short and can not be varied independently of water flow. In contrast, the contact time in a counter current protein skimmer can be adjusted by varying the rate at which water flows through the protein skimmer. Decades of research on foam fractionation has shown that the efficiency of a protion has shown that the efficiency of a protein skimmer can be expressed mathematically (see for example Guzman et al. 1986, Ahmad 1975 and Rubin et al1967). While a full exposition on the mathematics of foam fractionation is beyond the scope of this article, a key element of the mathematical model of foam fractionation is the relationship between the ratio of air flow to water flow. Mathemataical calculations and confirming experiments show that skimming efficiency increases as the ratio of gas flow to liquid flow (G:L) increases (Brunner and Stephan 1965). In one study, removal rates increased as the G:L ration increased and did not level out untill the ratio reached 16 (Ahmad 1975). The author wirtes, "only) above 16 the equilibrium of the separation process is reached and no futher effect takes place." In another study, removal rates continued to increase as G:L approached 10, the highest ratio measured. A third study of foam fractionation in aquaculture found that at a given water flow rate, the removal rate of volatile solids linearly increased as air flow increased (Weeks and Timmons 1992).
Most hobbyists who operate counter-current protein skimmers probably have no idea what their air to water ratio is. Unfortunately, most air pump manufactures do not publish the information necessary to make the calculations and most hobbyists to not have the tools to measure air flow. The Aquarium Frontiers (1994) Review of the first downdraft skimmer compared its performance to an air-driven counter-current protein skimmer with a water flow rate of 1200 liters per hour (Presumnably a pair of Tetta Luft pumps, a popular diaphragm air pump frequently recommended for large airstone-driven skimmers). The Luft pump is rated at 600 liters per hours, but it delivers considerably less air when driving wooden airstones. The actual air rate was probably less than 100 liters per hour during the author's tests. Even if we accept the author's estimations, the G:L ratio was no greater than 0.54 and probably much less. Given the extremely low G:L ratio, the counter-current skimmer was clearly far from optimized. It is no surprise the downdraft outperformed it. Rather than a measure of the effectiveness of the downdraft protein skimmer, the test demonstrated how poorly the hobby understands proper counter-current protein skimmer operation.
It would be helpful if manufacturers of protein skimmers would assist hobyists in the proper operation of skimmers, including the importance of a high air to water flow ratio. Although some recommend a water flow rate equal to the aquarium capacity, few offer recommendations regarding air flow rate. The ratio of air to water is more important than either flow rate by itself, so to make a recommendation regarding water flow rates without suggesting an air flow rate is virtually useless.
Authors who write for the hobby are another avenue for information on skimmer operation. Pherhaps the most complete exposition of protein skimming in the literature is found in The Reef Aquarium, Volume One (Delbeek and Sprung 1996). The authors devote 15 pages skimming operation and offer a handful of references should a hobbyist want to learn more. While Delbeek and Sprung make a number of suggestions on setting up a protein skimmer, here again there is little on the importance of the air/water ratio. The Modern Coral Reef Aquarium, Volume 1 (Fossa and Nilsen 1996) has a more abbreviated section on protein skimming, but the authors do at least state that the air output necessary for proper operation of an air-driven protein skimmer take getween 100 and 1000 liters of air per hour. However, their recommendation of one flow rate without the other rate is of little value to the hobbist. More recent reef aquarium books seem to have given up trying to help hobbyists set up protein skimmers all together. The authors of these books seem to be as befuddled by protein skimming as their readers. Because the G:L ratio has a great deal to do with the efficiency of protein skimming, hobbyists need to maximize the air to water ratio of their protein skimmers to get the most out of them. Water flow is fairly straightforward. Direct the return of the skimmer into acalibrated bucket and time how long it takes for the bucket to fill. Water flow and air flow need to be in the same units, so if water flow is measured in gallons, it need to be converted to liters or cubic feet, Air flow meters sold in the U.S. generally measure volume in cubic feet. One cubic foot of water equals 7.5 gallons. Once both water flow and air flow are in the same units, dividing the air flow by the water flow will indicate the G:L ratio for the protein skimmer. The Second Nature Supra 4 is an excellent air pump and one often recommended for airstone-driven protein skimmers, such as Pro 6500 from Marine Technical Concepts, the Supra 4 is capable of generating only 1 cubic foot of air per hour. A Tetra Luft Pump, oftensuggested for the this model and the pump used in the Aquarium Frontiers (Schiemer 1994) downdraft comparison, generates 3 cubic feet per hour powering the same skimmer.
I used a PRO-6500 for several years for my 90-gallon tank. Following the one tank volume per hour recommendation of 90 gallons per hour as my water feed rate (approximately 12 cubic feet of water per hour), and using a pair of Luft pumps to generatethe iar flow, would have translated into a G:L ratio of 0.50, far below the 10 to 16 ratio that would have maximized efficiency. For comparison, Marine Technical Concepts also manufacturers a similar-size venturi model that uses a Little Giant 3MDQ water pump for recirculation through the vneturi. The venturi draws 15 cubic feet per hour of air. Were I to use the same 90-gallon circulation rate, the venturi model G:L ratio would be 1.25, still below the ideal, but much better than the air-driven skimmer. Operationally, the venturi skimmer is the superior performer. However, in a perfect world, if you could optimize an air-driven skimmer it would be the best choice. But you can't, which is why venturi skimmers outperform air-dirven skimmers.
Marine Technical Concepts boasts that their HSA skimmer draws 70 liters of air with a water flow of 900 gallons per hour. That work out to be a G:L ratio of 1.2, essentially equal to their venturi model. However, while flow through the venturi model can be reduced to raise the G:L ratio, reducing the water flow through the HSA also reduces air flow. From my own observations andthose of other hobbyists, it appears that with a downdraft skimmer,air flow decreases at a faster rate than water flow. In other words, the G:L ratio declines as water flow is reduced. With an Iwaki 40RLT pump feeding an HSA protein skimmer, I measured the drawn air volume at 24 cubic feet per hour. That gives a G:L ratio of 0.26. Air does not flow as freely through the air flow meter as it does directly into the skimmer. The air normally drawn by the unit is probably greater, but in all likelihood, not enough to reach the 1.2 ratio of higher water flow rate-even if the actual air flow is double that measured, the G:L ratio remains well below the company's own counter-current skimmers. The decline in the G:L ratio as waterflow declines in a downdraft skimmer suggests that small downdraft skimmers are probably less effective than the larger downdraft skimmers that established the design's reputation. This means the smaller the hobbyist's tank, the greater the advantage of a counter-current skimmer. If a hobbyist with a 90-gallon tank followed the one tank volume per hour water flow recommendation and then tried to pump enough air through the proteins skimmer to attain the G:L ratio of only 5.0 he or she would need a pump capable of generating at least 60 cubic feet per hour of air, the equivalent of 20 Tetra Luft pumps! Clearly, using this many pumps is impractial. Instead, one could switch to a larger pump. piston air pumps are capable of generating considerably more air. For many years I used a pair of small poston air pumps distributed by Sandpoint that could generate 20 cubic feet per hour with the PRO6500. Unfortunately, piston air pumps tend to be noisy and considerably more expensive than diaphragm pumps. Even if one accepts the additional cost and noise, using large volumes of air runs counter to another foam fractionation principle. Protein skimmer efficiency decreases as superficial air velocity increases. Superficial air velocity is the air volumetric flow rate divided by the cross-sectional area of the protein skimmer (Chen 1994a). Ideal superficial velocities should b eless than 5 centimeters per second, a rather leisurely rise to the top for the generated bubbles (Shah et al. 1982). The reason protein removal efficiency decreases with increased air volume is twofold. First, as the air superficial velocity increases, bubble residence time decreases. Protein has less time to be adsorbed into air bubbles. The second reason is that as the superficial velocity increase, bubble size increases. Chen (1994b) found that protein removal decreases with bubble diameter. With the airstones typically used in the hobby the bubble size increases as the air velocity increases. The author found that as superficial air velocities changed from 0.75 to 4.5 centimeters per second,bubble diameter increased form 0.8 to 1.5 millimeters using Kordon silica airstones.
If a high ratio of air to water (G:L) is desirable, but high air velocities are undesirable, the solution is to first choose the air pump and then determine a water circulation rate through the skimmer that enables the hobbyist to achieve a high G:L ratio, Perhaps 2:1 for a start. If one uses a pair of Luft air pumps, a G:L ratio of 5 requires a water flow rate of only 9 gallons per hour. This is obviously a lot less than the one tank volume per hour conventional wisdom. However, using a low water flow and turning the water over more slowly will remove more protein than a higher flow rate maximizes contact time and increases teh air to water flow ratio, both critically important for maximizing protein skimming efficiency .
One note about comparing protein skimmer performance. Virtually all researchers have noted that the protein concentration of the water effects the performance of protein skimmers. First , bubble size decreases as protein concentration increases. This has to do with the different surface tensions on bubbles in different concentrations of protein. Second, protein skimmer effectiveness increases with increased protein concentration. "Protein does not concentrate enough in dilute solutions to form stable bubbles." (Sarkar et al. 1987) These two facts make it difficult to compare skimmer performance across tanks. Two hobbyists may get very different performances from the same protein skimmer set up similarly if the tanks differ in the concentration of protein. This phenomenon has probably added to the confusion over protein skimming-hobbyists have reported different results with apparently similar protein skimmer configurations. I have also found that ancillary equipment, such as check valves, air line tubing and other seemingly minor components, can have a significant impact on the efficiency of air driven protein skimmers.
To better understand the performance differences between downdraft and counter current protein skimmers, I conducted a series of tests similar to the those conducted in teh Aquarium Frontiers review(Schiemer 1994). A MAV Reef downdraft skimmer and Pro-6500 air-driven counter-current skimmer from Marine Technical Concepts were plumbed to a 30 gallon tank. The downdraft skimmer was driven by an Iwaki (130 cubic feet) per hour to the skimmer. At this water flow rate the injector drew approximately 20 cubic feet per hour, producing a G:L ratio of 0.15. The counter-current skimmer was fed by an Otto 2000 powerhead for a water flow rate of 30 gallons per hour (one tank volume) or 4 cubic feet per hour. The pair of poston air pumps mentioned earlier supplied air to two limewood airstones at a rate of 20 cubic feet per hour for a G:L ratio of 5.0. Both skimmers were allowed to mix and age for 72 hours. using a small powerhead.
Given the low -nutrient conditions, there was presumably little to skim. Extremely small bubbles (much less than 1 millimeter) filled the counter-current skimmer and made a slow spiraling ascent to the surface of the water column. Most bubbles would burst when they reached the surface, so virtually no foam was created. The downdraft skimmer, however, beganproducing substantial amounts of foam in a very short time. Within an hour, the downdraft had created a thick foam column that filled the riser tube. Where it not for the fact that the tank was virtually free of organics, one would assume the downdraft skimmer was outperforming the counter-current in removing organics. The ability to generate copious amounts of foam has been one of the key arguments in favor of downdraft skimmers. In this case, however, the amount of foam had nothing to do with its performance in removing organics. The bubbles in the lower portionof the downdraft riser tube were substantially larger than the bubbles in the counter-current skimmer. A high percnetage measured over 5 millimeters. The large size of bubbles rose they coalesced, with some reaching a size of 10 millimeters. The large size of bubbles suggested lower surface tension related to the absence of organics in the water. While the majority of bubbles in the counter-current skimmer rose, a large number of bubbles inthe downdraft moved downward. The turbulence of the waterflow seemed to create eddies that drew bubbles downward. This presumably increased contact time, althugh it was observed that many of these bubbles burst as they collided with other swirling bubbles. After operating for 24 hours, I added 500 milliliters of skimmate collected from my 300-gallon reef tank that I had previously measured at 100 milligrams per liter (mG:L) total nitrogen using the persulfate digestion method(D'Elia et al. 1977). Using published relationships between total nitrogen and protein in aquaculture, this created an effective protein level of approximately 3 mG:L protein in the tank, a level often found in aquaculture studies (Timmons 1994). Within a few minutes the counter-current protein skimmer began skimming and the foam in the downdraft skimmer became wetter and more uniform through out the column. Bth skimmers began producing considerable amounts of skimmate. The downdraft produced more skimmate, but lighter in color. The counter-current produced less skimmate, but of a darker color. The skimmate product of the two protein skimmers was fed back into the tank , giving the skimmers a continuous source of organics. In less than an hour the foam in the downdraft had collapsed and was less than half the height of the column before adding the skimmate. In contrast, the counter-current skimmer continued to skim.
Over the next several hours I found that by varying the flow rates of the two skimmers, I could effectively shut down either protein skimmer. If the downdraft skimmer was adjusted so foam flowed freely into the collection cup, the counter-current skimmer stopped skimming. If I adjusted the downdraft as a hobbyist normally would with foam just reaching the top of the riser tube, the counter-current would again begin skimming. After 24 hours, only the counter-current skimmer produced a dark-drown residue in the collection cup. After the first round of tests, the two small poston air pumps were replaced by a much large poston air pump rated at 60 cubic feet per meter that generated 52 cubic feet of air per hur feeding two limewood airstones. This mean the counter-current skimmer now had a G:L ratio of 13. With this ratio of air to water, foam filled the top 18 inches of the reaction chamber. The downdraft skimmer foam collapsed and no adjustments could get it to again produce foam.
The counter-current skimmer was drained and the MAV downdraft skimmer was replaced with the HSA skimmer from Marine Technical Concepts and an Iwaki 40RLT pump. The HSA downdraft skimmer uses a slightly different design, but is very similar to other downdraft skimmers in principle. Water flowing at a high velocity is forced through a narrow aerator that draws air into the water flow. The air-water mix flows into a reaction chamber where the foam is generated. Whiel the E.T.S. skimmer has a separate "downdraft" and reaction chamber, the HSA downdraft tube is within the reaction chamber. This makes for a more compact unit, but the design creates more turbulenceat the air-water interface than with the E.T.S. models. The HSA was run alone until it was consisently producing foam-approximately two days. At that time, the counter-current skimmer was again turned on. Within a few minutes the counter-current skimmer was producing large amounts of foam and the HSA ceased foam production. Because all three designs could produce foam independently, and each affected the others operating at the time, the "shutdown" reports of hobbyists who used downdraft early on may not be as significnat as they first appeared. Small perturbations in a reef tank have long been know to affect skimmer operation. Adding food to a tank and even just putting one's hand in the tank will stop most skimmers from working. Adding a second skimmer of any sort appears to have the same impact on the performance of existing skimmers. Does this mean that using multiple skimmers on the same tank will not work? Not nexessarily. I have used combinations of counter-current skimmers for years with good results. Public aquarium routinely use multiple protein skimmers operating in parallel. The key is to combine skimmers with similar efficiencies.
THE UPDRAFT SKIMMER
One disadvantage of using an air driven counter-current protein skimmer is the need to periodically replace the wooden airstones. Wooden airstones produce much finer bubbles than bonded glass airstones, but they also deteriorate much faster. One trick with downdraft skimmers is to use bioballs to break up large bubbles so that by the time the water reaches the reacton chamber, only small bubbles remain. I wondered if the same approach could be applied to counter-current skimmers. I replaced the wooden airstones with bonded glass airstones and then filled the reaction chamber with bioballs. Using the large piston air pump with glass airstones produced very large bubbles, similar to those generated by the HSA skimmer. They rose through the water very quickly, but because of the bioballs, a large percentage of teh bubbles caromed through the skimmer bouncing from bioball to bioball like a ball in a pinball machine. Without the bioballs, the combination of large bubbles and high volumes of air produced a very unstable , frothy air-water interface. With the bioballs, the air-water interface was much more stable and the skimmer was able to produce large amounts of foam.
Using Methods and techniques first developed for downdraft skimmers may make it possible to eliminate wooden airstones and make counter-current skimmers more convenient to use. It is clear that we need to rethink the belief that downdraft protein skimmers are superior to counter-current skimmers. I believe counter-current skimmers can perform as well, if not better, than downdraft skimmers if they are properly turned, and they have several advantages. We also need to rethink how we evaluate protein skimmers. The ability to generate foam may not be the best indicator of protein skimmer effectiveness. Downdraft skimmers are capable of producing large quantities of foam in the absence of organics. In addition, I found that darker colored skimmate contained a lower concentration of total nitrogen than thin water skimmate. Protein skimmers can be effective mechanical filters, and green "sludge" hobbyists commonly point to as a measure of a skimmer's effectiveness may be particulate matter that would better serve as food for filter-feeding organisms. The best removal of dissolved organic may, in fact, be in the wet, nearly clear, foam hobbyists have typically avoided.
Ironically, the protein skimmer arms race has spawned its own peace movement whose members are against the use of protein skimmers for reef tanks. The peace movement believes that protein skimmers remove too many desirable molecules along with the undesirables. Many corals feed on bacteria, dissolved organics (Sorokin 1991). Excessive protein skimming can remove virtually all of these potential food sources, to the detriment of the tank's inhabitants. Any protein skimmer can create these problems, but excessively powerful protein skimmers can exacerbate the problem. Counter-current protein skimmers can be "detuned" by lowering the G:L ratio. Increasing water flow or decreasing air flow to the skimmer will reduce its efficiency and enaable the hobbyist to determine the rate at which skimming takes place. By watching the inhabitants of the tank as adhystnebts are made to the skimmer, one can find a balance between excessive organics removal and inadequate removal. Then, if at some point in the future the hobbyist needs more rapid removal of organicsm he or she can vary water or air flow to increase the G:L ratio. Downdraft protein skimmers are innovative engineering marvels, and the many successful reef tanks using them speak to their effectiveness. They are technological breakthroughs that demonstrate that there are more ways to create an air/water mix than airstones and venturis. Their apparent performance advantage, however, is more and indicator of the hobby's failure to understand foam fractionation and the meansto optimize the performance of counter-current skimmers, rather than the downdraft skimmer's inherent superiority. Hobbyists should resist getting caught up in the unbridled exuberance that can sweep reekeeping when technological "breakthroughs" capture the imagination of other hobbyists.
Copy from Marine Fish USA and Reef 1999 ANNUAL Page56~66
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