mr_z
New member
http://www.wetwebmedia.com/proskimrart2.htm
Air-Driven: Air-Driven skimmers were the first models to enter the hobby in co-current (air flowing with the direction of feed water: a poor design for aquariums) and counter-current styles (air flowing against the direction of feed water: a better design for aquariums). They may be internal or external in nature, and gravity fed or pump fed. These simple units use air bubbles produced by strong air pumps and generally wooden air stones. Even though they are called air-driven, some come with a water pump that feeds the skimmer raw water to be processed. Most modern incarnations of this style are a counter-current design. Essentially, this means that water enters near the top of the skimmer and exits from the bottom while tiny air bubbles are injected near the bottom and work their way to the top with resistance from the water flow which increases contact time and strips proteins from the raw water. Counter-current air-driven protein skimmers can be very efficient at removing significant amounts of quality skimmate. They have lost favor with some hobbyists because of their dependency on sometimes frequent maintenance and adjustments. Wood air stones decay over time, which results in increased backpressure, decreased bubble production, and less skimmate extracted. I recommend the replacement of wood air stones monthly or better to maintain optimum performance. Another drawback to air-driven skimmers is the need for an air pump. They can be noisy and generally use a rubber diaphragm to pump the air. These diaphragms degrade if not rupture in time. While they last considerably longer than wood air stones, at a year or more for most, this is another aspect of maintenance and upkeep to consider.
Advantages to Air-driven skimmers:
? Generally inexpensive to buy and easy to install
? Simple adjustments and predictable skimmate production with proper installation
? Many tried and true DIY plans available abroad for the ambitious and crafty
Disadvantages to Air-driven skimmers:
? Often labor intensive with sometimes daily adjustments needed to maintain skimmate production
? Wood airstone are limiting as a natural product with variations in quality and longevity by batch
? Ongoing expense of airstones and air pump diaphragms
? Must be exceptionally tall to serve large systems
Venturi:Venturi air-injection was the next big technological development in the evolution of marine aquarium protein skimmers. A venturi is a specially designed piece of plumbing with a profile that resembles an inverted "T". Water is forced through at high velocity, which causes a low-pressure suction on the open stem (top) of the inverted T and draws air in. You may have noticed this feature on powerhead water pumps. In this application, venturis are used to inject air into their water stream to aid in oxygenation. In this application they are rather crude devices, but you get the picture. Protein skimmer venturi valves, however, are high precision instruments engineered to produce a very fine-sized air bubble. The better ones also come with a threaded needle control valve for fine-tuning the amount of air injected into the skimmer. The venturi-driven skimmers were a significant improvement over air-driven skimmers. The keystone of a good, simple venturi skimmer is the water pump that drives both the air and water flow, ideally, with great consistency. This should translate into less maintenance/adjustment (perhaps weekly instead of daily) for the aquarist and more reliable skimmate produced. In contrast, air-driven skimmers may require you to adjust both the amount of air and water fed into the contact chamber, which can complicate attempts at producing dark skimmate consistently. Venturi skimmers require that their water pump be cleaned frequently, like any water pump, of buildup (bacterial slime and mulm) on all interior parts and surfaces. You will also need to periodically clean the venturi stem of dust and debris like salt creep or scale that accumulate. Comparatively, venturi style skimmers cost a little more than air-driven models, but for that extra money, they should produce more skimmate regularly if designed well.
Advantages to Venturi skimmers:
? Well-designed models are a better value than air-driven models: a lot more production for little extra cost
? Some good designs are available and affordable for systems on a budget
? Lower maintenance and no significant expense of upkeep (no air stones or pump diaphragms)
? Most designs occupy comparatively less space: compact units are available and worthy
Disadvantages to Venturi skimmers:
? The hobby market is flooded with inferior models in this style (research your brand and prospects well!)
? A reduced contact time in compact models demands properly delivered feed water for efficient skimming (this has been addressed/corrected in some models with extended contact centrifugal chambers)
Aspirating The next leap in skimmer design brought us the aspirating models. These differ from a venturi in principle by pulling air through a pump impeller on the intake side (aspiration then fractionation) instead of drawing air from the output side of a water pump via the rush of exiting water. Basically, an aspirating pump sucks in air with water, uses the impellor to "chop up" the air into finer bubbles, and then injects this foamy mixture into the contact chamber. The price range of this style runs the gamut from some of the least through the most expensive skimmers on the market. Unfortunately, some of the cheapest ones out there also tend to be some of the worst performing skimmers. The difference, primarily, is in the size of the unit and the design of the impellor. Needle-wheel impellors are very different from the standard impellor used in some aspirating models. Modification of the impellor allows an aspirating model to efficiently blend air and water more effectively and produce smaller and more consistent bubbles. Now the question arises, why don't all aspirating skimmers use needle-wheels or perform similarly? The answer is needle-wheels are a patented technology. It costs real money to license and produce this kind of hardware. The higher end skimmers of this style are very effective, easy to adjust, easy to clean, and moderately sized (modest spatially).
Advantages to Aspirating skimmers:
? Top shelf models are categorically consistent and reliable (bubble size, skimmate production, etc.)
? Lower maintenance and no significant expense of upkeep (no air stones or pump diaphragms)
? Most occupy comparatively less space than other styles in their competitive price and efficiency range
Disadvantages to Aspirating/Needle skimmers:
? Like venturis, the market is flooded with inferior models in this style (research your brand and prospects well!)
? Even infrequent cleanings of the delicate needle-wheels are precarious. Damage to them can be expensive to repair or replace
Downdraft
owndraft skimmers are some of the most powerful skimmers available and quite popular with large home aquariums. They use a big pump to inject water down a narrow tube at high velocity. This thin tube usually has bioballs or like media in it. These are not intended for biological filtration, although some bacteria will inevitably develop there and participate in biological filtration. The real purpose of this media is to whisk water through the baffles (bio-balls) at a high speed to create ultra fine bubbles like whitewater in rapids. The crashing water forced through the bio-balls creates very effective foam, which is then channeled into a box below before continuing on its way to rise and accumulate skimmate via a larger reaction chamber. Downdraft skimmers are inherently expensive due to their large size, raw materials needed for production (thick acrylic), and the amount of skilled craftsmanship needed for fabrication. They also require a large water pump, which adds to both their initial cost and ongoing operational expenses; for many smaller tanks they are overkill with regard for efficacy and purchase price. Most units are also somewhat to very unfriendly to clean and service routinely (recessed and inaccessible regions, tedious thumb screws for disassembly, etc). On the positive side, however, they are relatively easy to adjust and perform exceptionally well on large systems with heavy bioloads.
Advantages to Downdraft skimmers:
? Consistent and reliable bubble size and skimmate production
? Well suited for large aquariums and heavy bio-loads
Disadvantages to Downdraft skimmers:
? Expensive to purchase and operate
? Difficult to clean and service
? Necessarily large and cumbersome by design
? A poor value for performance versus price paid (more "bang for your buck" on other styles)
? Noise of operation is can be an issue for some aquarists
? The large pumps required impart significant heat to system. This can be dangerous for systems already operating on a precarious threshold.
Air-Driven: Air-Driven skimmers were the first models to enter the hobby in co-current (air flowing with the direction of feed water: a poor design for aquariums) and counter-current styles (air flowing against the direction of feed water: a better design for aquariums). They may be internal or external in nature, and gravity fed or pump fed. These simple units use air bubbles produced by strong air pumps and generally wooden air stones. Even though they are called air-driven, some come with a water pump that feeds the skimmer raw water to be processed. Most modern incarnations of this style are a counter-current design. Essentially, this means that water enters near the top of the skimmer and exits from the bottom while tiny air bubbles are injected near the bottom and work their way to the top with resistance from the water flow which increases contact time and strips proteins from the raw water. Counter-current air-driven protein skimmers can be very efficient at removing significant amounts of quality skimmate. They have lost favor with some hobbyists because of their dependency on sometimes frequent maintenance and adjustments. Wood air stones decay over time, which results in increased backpressure, decreased bubble production, and less skimmate extracted. I recommend the replacement of wood air stones monthly or better to maintain optimum performance. Another drawback to air-driven skimmers is the need for an air pump. They can be noisy and generally use a rubber diaphragm to pump the air. These diaphragms degrade if not rupture in time. While they last considerably longer than wood air stones, at a year or more for most, this is another aspect of maintenance and upkeep to consider.
Advantages to Air-driven skimmers:
? Generally inexpensive to buy and easy to install
? Simple adjustments and predictable skimmate production with proper installation
? Many tried and true DIY plans available abroad for the ambitious and crafty
Disadvantages to Air-driven skimmers:
? Often labor intensive with sometimes daily adjustments needed to maintain skimmate production
? Wood airstone are limiting as a natural product with variations in quality and longevity by batch
? Ongoing expense of airstones and air pump diaphragms
? Must be exceptionally tall to serve large systems
Venturi:Venturi air-injection was the next big technological development in the evolution of marine aquarium protein skimmers. A venturi is a specially designed piece of plumbing with a profile that resembles an inverted "T". Water is forced through at high velocity, which causes a low-pressure suction on the open stem (top) of the inverted T and draws air in. You may have noticed this feature on powerhead water pumps. In this application, venturis are used to inject air into their water stream to aid in oxygenation. In this application they are rather crude devices, but you get the picture. Protein skimmer venturi valves, however, are high precision instruments engineered to produce a very fine-sized air bubble. The better ones also come with a threaded needle control valve for fine-tuning the amount of air injected into the skimmer. The venturi-driven skimmers were a significant improvement over air-driven skimmers. The keystone of a good, simple venturi skimmer is the water pump that drives both the air and water flow, ideally, with great consistency. This should translate into less maintenance/adjustment (perhaps weekly instead of daily) for the aquarist and more reliable skimmate produced. In contrast, air-driven skimmers may require you to adjust both the amount of air and water fed into the contact chamber, which can complicate attempts at producing dark skimmate consistently. Venturi skimmers require that their water pump be cleaned frequently, like any water pump, of buildup (bacterial slime and mulm) on all interior parts and surfaces. You will also need to periodically clean the venturi stem of dust and debris like salt creep or scale that accumulate. Comparatively, venturi style skimmers cost a little more than air-driven models, but for that extra money, they should produce more skimmate regularly if designed well.
Advantages to Venturi skimmers:
? Well-designed models are a better value than air-driven models: a lot more production for little extra cost
? Some good designs are available and affordable for systems on a budget
? Lower maintenance and no significant expense of upkeep (no air stones or pump diaphragms)
? Most designs occupy comparatively less space: compact units are available and worthy
Disadvantages to Venturi skimmers:
? The hobby market is flooded with inferior models in this style (research your brand and prospects well!)
? A reduced contact time in compact models demands properly delivered feed water for efficient skimming (this has been addressed/corrected in some models with extended contact centrifugal chambers)
Aspirating The next leap in skimmer design brought us the aspirating models. These differ from a venturi in principle by pulling air through a pump impeller on the intake side (aspiration then fractionation) instead of drawing air from the output side of a water pump via the rush of exiting water. Basically, an aspirating pump sucks in air with water, uses the impellor to "chop up" the air into finer bubbles, and then injects this foamy mixture into the contact chamber. The price range of this style runs the gamut from some of the least through the most expensive skimmers on the market. Unfortunately, some of the cheapest ones out there also tend to be some of the worst performing skimmers. The difference, primarily, is in the size of the unit and the design of the impellor. Needle-wheel impellors are very different from the standard impellor used in some aspirating models. Modification of the impellor allows an aspirating model to efficiently blend air and water more effectively and produce smaller and more consistent bubbles. Now the question arises, why don't all aspirating skimmers use needle-wheels or perform similarly? The answer is needle-wheels are a patented technology. It costs real money to license and produce this kind of hardware. The higher end skimmers of this style are very effective, easy to adjust, easy to clean, and moderately sized (modest spatially).
Advantages to Aspirating skimmers:
? Top shelf models are categorically consistent and reliable (bubble size, skimmate production, etc.)
? Lower maintenance and no significant expense of upkeep (no air stones or pump diaphragms)
? Most occupy comparatively less space than other styles in their competitive price and efficiency range
Disadvantages to Aspirating/Needle skimmers:
? Like venturis, the market is flooded with inferior models in this style (research your brand and prospects well!)
? Even infrequent cleanings of the delicate needle-wheels are precarious. Damage to them can be expensive to repair or replace
Downdraft
owndraft skimmers are some of the most powerful skimmers available and quite popular with large home aquariums. They use a big pump to inject water down a narrow tube at high velocity. This thin tube usually has bioballs or like media in it. These are not intended for biological filtration, although some bacteria will inevitably develop there and participate in biological filtration. The real purpose of this media is to whisk water through the baffles (bio-balls) at a high speed to create ultra fine bubbles like whitewater in rapids. The crashing water forced through the bio-balls creates very effective foam, which is then channeled into a box below before continuing on its way to rise and accumulate skimmate via a larger reaction chamber. Downdraft skimmers are inherently expensive due to their large size, raw materials needed for production (thick acrylic), and the amount of skilled craftsmanship needed for fabrication. They also require a large water pump, which adds to both their initial cost and ongoing operational expenses; for many smaller tanks they are overkill with regard for efficacy and purchase price. Most units are also somewhat to very unfriendly to clean and service routinely (recessed and inaccessible regions, tedious thumb screws for disassembly, etc). On the positive side, however, they are relatively easy to adjust and perform exceptionally well on large systems with heavy bioloads. Advantages to Downdraft skimmers:
? Consistent and reliable bubble size and skimmate production
? Well suited for large aquariums and heavy bio-loads
Disadvantages to Downdraft skimmers:
? Expensive to purchase and operate
? Difficult to clean and service
? Necessarily large and cumbersome by design
? A poor value for performance versus price paid (more "bang for your buck" on other styles)
? Noise of operation is can be an issue for some aquarists
? The large pumps required impart significant heat to system. This can be dangerous for systems already operating on a precarious threshold.