Related FAQs: Marine Physical Filtration,  Ozone & Ozonizers 1, FAQs 2, Ultraviolet Sterilizers, Ultraviolet Sterilizers 2, Ultraviolet Sterilizers 3, UV Use in Business Set-Ups, Magnetic Field Filtration, Wet Dry Filters and Protein Skimmers, Outside Power Filters, Canister Filters,  FAQs 2,  Canister Filters 3, Related Articles: Marine Aquarium Filtration, by Adam Cesnales, Skimmers by Steven Pro, Marine Set-Up, Marine Filtration, Mechanical & Chemical, Redox, Review of the ViaAqua Canister Filter, Protein Skimmer Impressions By Steven Pro, Power Filter Impressions,  A review of some popular mechanical filtration systems by Steven Pro,   /The Conscientious Marine Aquarist Protein Skimming, Ozone, and UV Use in Marine Filtration

By Bob Fenner

Sanders Ozonizer, properly installed

Quick, in the way of filtration, tell me what's absolutely essential. If you said biological, go to the head of the class. Now tell me what type of filtration would you next employ after making sure your nutrient cycling bases we're covered. Ah, that's not so easy; or is it? Ever heard such statements as "time marches on?" Well, in the case of the best available, most appropriate marine system filtration, time seems to have taken a burp backward.

Back in the heyday of aquarium interest in the U.S.; the sixties into early seventies, protein skimming with and without the use of ozone gained popularity. Indeed, many European countries got out of the chlorination business for treating tap water, and took up ozone in it's place. Somehow these physical filter tools lost their popularity in the West. Some writers speculate that pet-fish retailers were to blame; that selling more livestock, carbon... was more profitable than these one-time cost investments. Who really cares "whose to blame?" Ridiculous.

I don't really know the origin of this "discontent", but I do know that every captive marine system can benefit supremely through their use.

Protein skimmers or foam fractionators

Are, in my opinion, an absolute necessity for any marine system. Beyond requisite biological filtration, nothing is better at improving water quality; nothing.

The bulk of undesirable organic wastes that we want to eliminate from our systems are "surface-active", collecting near the surface of a gas-liquid interface. This affinity can be capitalized in a column of aquarium water with air bubbles mixed in. Trapped materials, including wastes, uneaten food and more are subsequently collected at the top as foam. These tools are therefore referred to as foam separators, fractionators, air-strippers, or protein skimmers.

Efficiency of a unit depends on several factors, notably air-water contact time and bubble size. The greater the former and smaller the latter, the better. In addition there are adjuncts, especially ozone, that can add greatly to removal per pass.

Now, I want you to take a big breath with me (relax, open your mind) and follow along: Yes, counter-current flow (with new water meeting the opposite direction as up-flowing bubbles), venturi (with air and water swooshing around in a vortex, increasing contact time), taller (versus shorter) protein skimmers are better then other short, regular (co-current) flow, non-venturi units. The question to you, the consumer/hobbyist has got to be, "How much better?" The most pathetic, under-powered, clogged airstone, in-tank unit is better than none. The super-duper, no-lie, hand-shake, dyed-in-the-wool measure of whether your particular set-up can be determined by two easy observations: 1) After feeding, and cleaning does your skimmer system collect a whole bunch of material and at some point stop, as in dry and/or no foam?, and 2) If when #1 happens does trying another unit really foam up on what's left? As the saying goes, AH, HaH!

Airstones and the air pump to supply them present a "what came first the chicken or the egg?" dilemma. Sure, you'd like to maximize your air volume while minimizing bubble size; but they're mutually exclusive goals. The best you can do is to have the most air flow you can with ideal, consistent bubble size (@ 1/2 millimeter). Glass and wood airstones work great when new/clean. Keep your eye on them and have at least two sets, one in use, and the other for cleaning/air-drying to extend their functional/useful life. Please see pertinent notes below under Ozone, Dedicated air.

In Tank Models: I'm not a big fan of these on two counts. After you've collected all that yucky gunk, you don't want to spill any back into your system; it's smelly and probably more toxic than when it was collected. In-tank (and in-filter-sump) protein skimmers are just too easy to do this with to suit me.

Secondly, most are too puny to do much good. See above. Taller, functional units (except for some squat venturi types) are just too big to fit into the systems they service. All this being said, if all you can fit in or afford is an in-tank model, make it a good one, and be vigilant in servicing it.

Loss of Essential Matter is a concern the hobby literature has non-addressed over and over. There is very little in the way of trace elements, therapeutics, and more that has been determined scientifically to be removed by skimming. New materials are constantly added with foods, biological activity and water changes. Except for "run-in" periods (the first few weeks) to establish nutrient cycling, I advocate full-time operation of your skimmer. You cannot "over-skim" a tank. Loss of Essential Matter is a concern the hobby literature has non-addressed over and over. There is very little in the way of trace elements, therapeutics, and more that has been determined scientifically to be removed by skimming. New materials are constantly added with foods, biological activity and water changes. Except for "run-in" periods (the first few weeks) to establish nutrient cycling, I advocate full-time operation of your skimmer. You cannot "over-skim" a tank.

Maintenance: Your daily rounds of inspecting your system should include checking on the skimmer and emptying the collector cups contents. Depending on the model and whether or not you use ozone (see below) to enhance the skimmers efficiency, there is a need for periodic cleaning. Power (venturi) skimmers with ozone are the most maintenance-free; others require weekly to monthly brushing to remove proteinaceous slime build-up on their walls.: Your daily rounds of inspecting your system should include checking on the skimmer and emptying the collector cups contents. Depending on the model and whether or not you use ozone (see below) to enhance the skimmers efficiency, there is a need for periodic cleaning. Power (Venturi) skimmers with ozone are the most maintenance-free; others require weekly to monthly brushing to remove proteinaceous slime build-up on their walls. 

Ummm...

In Summary: with it's low initial and operating cost, high efficiency of operation in removing organics, with concomitant reduction in bio-load, algal growth, enhanced water quality, a protein skimmer can effectively eliminate the problems related to waste accumulation in a marine system. I wouldn't have a tank without one. In Summary: with it's low initial and operating cost, high efficiency of operation in removing organics, with concomitant reduction in bio-load, algal growth, enhanced water quality, a protein skimmer can effectively eliminate the problems related to waste accumulation in a marine system. I wouldn't have a tank without one.

Ozone:

Sometimes called the "purest form of oxygen", ozone, O3 is a highly unstable tri-atomic molecule. It's the smell that's so fresh after an electric storm, the crispness in the air in and around large electric motors; it can be a boon to you in "burning" up organics and microbes, raising pH, dissolved oxygen and Redox, and most importantly, boosting the efficiency of your protein skimmer.

How It's Made: By an ozonizer, through a process called ozonolysis; okay, sorry to be so smart-alecky. Older, low-production units utilize a germicidal lamp, such as those in U.V. sterilizers. The higher yield, more modern models use a corona discharge (electrical) method of making ozone.

How It's Applied: The optimal application of ozone is through your skimmer, with the water's discharge back to a sump (usually a filter) for mixing, out-gassing, and chemical filtration before return to the main system.

Dedicated air: feeder systems to skimmers come in two formats, pressurized air and venturi. With the latter air is drawn in by partial vacuum, the first involves an air pump. What type? A strong, quiet, dedicated one; that is one that is only operating the skimmer. This is necessary to avoid "adjustment headaches", a condition you will get if you chintz and try to gang other outlets with your not-so-dedicated skimmer air pump.

Whether you have a pumped air or venturi delivery, you should utilize a good check valve to prevent "back-siphoning" through capillation, and ozone resistant tubing. If you are or become a total fanatic, you can even increase your ozone production efficiency with an air dryer. Let me hasten to add that, yes, ozonizers work fine without air-dryers (but better in low humidity air), and double-yes, protein skimmers work fine without ozonizers (though not as "efficiently").

Ozone Dangers: Numerous authors cite the need for carbon filtration, venting to prevent ozone poisoning of livestock, and even hobbyists (!). These fears are largely unfounded. Though I would not directly introduce ozone into a system, the little that intended units produce is dissipated quickly when utilized in a skimmer. The worst that does occur with small ozone generators is increased corrosion of "rubber" materials in your system; well worth the many benefits. You, your fishes and house will not burn up or down, I promise.

My Overall Ozone Opinion: The chemical degradation of large organic molecules, responsible for off-color, turbidity, low oxygen and some toxicities by ozone make it's small start-up and operational costs pale. If you're even vaguely considering an investment in any sort of meter, doser, denitrator, ultraviolet sterilizer... STOP, do not proceed to go; buy and use a small ozonizer in conjunction with your skimmer first. Almost all public aquaria utilize ozone with theirs; you should to. The chemical degradation of large organic molecules, responsible for off-color, turbidity, low oxygen and some toxicities by ozone make it's small start-up and operational costs pale. If you're even vaguely considering an investment in any sort of meter, doser, denitrator, ultraviolet sterilizer... STOP, do not proceed to go; buy and use a small ozonizer in conjunction with your skimmer first. Almost all public aquaria utilize ozone with theirs; you should to. 

Ultraviolet Sterilizers: Use in Filtration Systems

Ultraviolet (U.V.) radiation is sometimes employed in water purification systems for tropical freshwater, marine, cool water and pond systems. U.V. sterilization can be very effective in reducing free-floating algae, bacteria and other microscopic planktonic organisms. A U-V sterilizer should be of limited value in a properly set-up and operated marine system. Too many people are of the opinion that zapping their water with a ultraviolet device confers some "holy grail" water quality improvement. This is not the case. An adequately sized U-V for the volume of water in a system and rate of post-filtered flow will improve water quality nominally in terms of lowering overall free-floating microbe levels. Additionally there is a slight improvement in dissolved oxygen, oxidation of metabolites, ozone production and skimmer efficiency. It is up to the individual aquarist to decide whether this incremental improvement is worth the cost in procurement, electrical consumption, bulb replacement and maintenance.

Details of U-V Benefits:

UV and near UV radiation, 295 to 400 nm (nanometers) has also been documented to aid in oxidation of organics, phosphate and nitrogenous compounds through the collateral production of ozone (O3).

Though the disease-reducing benefits above are considerable in producing and maintaining a favorable environment, UV sterilization should not be relied on as the principal part of a filtration system. UV purification can be a very useful addition to an otherwise appropriate filtration system. Ideally a UV will reduce microbial levels to, or below those in the wild. Population explosions of these organisms are most prevalent in new, disturbed systems, and one's where bio-load/feeding is concentrated and vacillating. Hence the extensive use of UV in wholesale operations.

Cons:

UV light is indiscriminate in the destruction of free-floating micro-organisms. It kills "good guys" as well as bad. These beneficial microbes are absolutely necessary in almost all captive environments. For this reason: 1) Initial, break-in periods of new aquatic set-ups are run without the UV being turned on. 2) It is suggested that UV's be left off in conjunction with some therapeutic treatments, but can be used with others.

Organisms maintained in a "well-filtered", strongly UV sterilized system seem to develop a type of acquired immune deficiency syndrome. Like the boy-in-a-bubble, organisms kept in an almost sterile environment seem to lose their ability to ward off infectious diseases. Now, let me explain the qualifiers placed upon the terms above. A) There are no captive systems that result in 100% effective kill of all micro-organisms. B) This loss of apparent immunity occurs over long periods of time in a highly variable, non-selective manner. C) This "syndrome" has, to my knowledge, never been scientifically documented; therefore my use of the word seems from my personal and second-hand experiences.

Application:

UV purification is widely used in many industries; medical, recreational swimming, alcoholic beverages and drinking water purification applications among others.

UV light is a natural part of electro-magnetic-radiation (EMR); in terms of frequency it is of shorter wavelength than visible light.

There are sizes, fittings and models of UVs for virtually any aquatic application; freshwater and marine aquaria, pools, ponds and re-circulating multiple tank systems.

The water going through the U.V. sterilizer should first be run through biological filtration and mechanically filtered to remove particulates. Allowing air bubbles or any solid matter to pass through the contact chamber is contra-indicated. For this reason, using an air-lift system as a means of moving water through the U.V. is a very poor idea. It is suggested that if a heat-exchanger and/or separate chemical filtration is utilized that these come before the U.V.. In other words, the U.V. system should be the last part of the filtration system to have water passed through before returning to the live-holding systems. The reasons for this are several and mostly obvious. The most important are:

1) To remove as much "other stuff" from the water so that the U.V. radiation will operate with highest efficiency.

2) Beneficial microbes will be preserved and their activity promoted.

An Idealized Filtration System

Flow Rates:

Dwell time, the amount of time a given quantity of water is exposed to a given concentration of radiation may be roughly gauged at about twenty gallons per hour flow per watt U.V.. This value or more watts per unit flow is adequate for providing a good kill rate per pass and will substantially reduce planktonic micro-organisms and organics concentrations.

The beneficial effects of U.V. are enhanced by utilizing the filter system order described above and by arranging for as complete a circulation pattern as possible in your live-holding system. More vigorous flows are not necessarily to be avoided, but reducing dwell time will result in loss of efficiency per pass. Passing all the water in the system though the filter mechanisms once or more an hour is ideal.

Sleeves:

Most U.V. lamps are engineered to operate at around 72 degrees Fahrenheit. Cooler water systems or systems with debris or pressure that might damage the lamps can be fitted with sleeves of quartz of Teflon. All serious ultraviolet sterilizers are fitted with sleeves. They aid in efficient transmission of the proper wavelengths, extend bulb-life, and greatly ease periodic cleaning.

These jackets require periodic inspection and cleaning as for the lamps in (non-sleeved) tropical systems that come in direct contact with the water.

Plumbing Layout:

Figure 3: To facilitate cleaning and lamp replacement, the following layout is offered:

Valves A and B can be closed after opening C, allowing continuous operation of the system during U.V. shutdown. Multiple U.V. systems can be cut in parallel to aid in cleaning one at a time.

Maintenance:

Regular, routine up-keep is necessary to assure peak performance. Sleeves &/or bulbs should be removed from their contact chambers and cleaned once a month or so. Generally, this can be accomplished by simply wiping with a clean, dry cloth or towel. If necessary, slime may be removed by wiping with rubbing alcohol.

To Build or Buy a U.V.?

Depending on the size and complexity of the system in question, an adequate U.V. might cost as little as $80.00 to buy and $60.00 to build, with the ratio of cost to savings improving with the size of the system. This guesstimate, of course, figures no charge for your tools and your time to search for, collect and assemble the necessary components.

To Build: To Build: A simple do-it-yourself model is described below; assembled with easy to find parts and solvent.

Parts:

1) 1+ fluorescent fixture(s); connectors, ballast, switch, cord, wire.

2) 1+ germicidal (U.V.) lamp; from medical, pet fish business.

3) Some plastic (PVC, ABS) pipe of adequate diameter to allow insertion of lamp, possibly sleeve and permit water flow.

4) Fittings; tees, reducers, barbs if necessary.

5) 2+ compression fittings for water-tight sealing of lamp and/or sleeve.

6) Possibly quartz or Teflon tubing for sleeves.

7) A pumping source for pushing/pulling water through the UV.

Figure 2: Ersatz Home-Made Ultraviolet Sterilizer

Buying a U.V.: Features to look for:

1) Remote-able ballast; to position it in a heat and water-damage free pace.

2) Indicator light; to check for "on" operation.

3) Automatic on feature; to turn the UV back on in the event of a temporary power loss.

4) Couplings that are easily fitted to your system.

5) Sleeves at little or no additional cost.

6) Guarantees/warrantees.

7) All non-corrosive, water-contact surfaces.

8) Ask other user's regarding their success/failure, in particular with leakage and ease of use with given brand names and models.

Bibliography/Further Reading:

Protein Skimming/Foam Fractionation:

Anderson, Bryce P. 1971. Protein skimmer. Marine Aquarist 2(4):71.

Dyer, Scott & J. Charles Delbeek. 1991. To skim or not to skim? That is the question; understanding and using protein skimmers can make all the difference. AFM 1/91.

Escobal, Peter R. 1995. Inside protein skimmers; more than you ever wanted to know. AFM 2/95.

Giovanetti, Thomas A. 1988. Protein skimmers and ozone in marine aquaria... their use and maintenance. FAMA 5/88.

Giovanetti, Thomas A. 1991. How to evaluate a protein skimmer. TFH 11/91.

Goldstein, Robert J. Protein skimmers; innovative thinking and modern technology make them jewels among aquarium products. Pet Age 11/93.

Greco, Frank. 1987. The living reef, comments on miniature coral reef systems. Part one: protein skimming and ozonation. FAMA 9/87.

Keith, Randy E. 1980. Protein skimmers in the marine aquarium. FAMA 9/80.

Lemkemeyer, Jurgen. 1988. The marine aquarium; possible without a skimmer? Today's Aquarium 1/88.

Montgomery, Bill. 1990. The misunderstood co-current protein skimmer. FAMA 5/90.

Nilsen, Alf Jacob. 1990. The successful coral reef aquarium, part 1: protein skimming. FAMA 8/90.

Thiel, Albert J. 1992. Servicing your protein skimmer. FAMA 10/92.

Wilkens, Peter. 1992. Technological overkill? Skimmers and trickle filters: pros and cons. TFH 2/92.

Ozone:

Scoville, Paulette. 1994. Using ozone to improve your aquarium's Redox potential can be easy. FAMA 5/94.

Steslow, Frank A. 1991. Ozone kinetics in seawater. FAMA 11/91.

Ultraviolet Sterilizers:

Cross, Verlin K. and Lee Peterson. 1987. Efficacy of ultraviolet water treatment at the Green Lake, Maine, National Fish Hatchery. The Progressive Fish Culturist 49:233-235/87.

Drew, C. 1970. How To Build an Ultra-Violet Germicidal Filter. Modern Aquarium, December 1970.

Epps, John E. 1993. Ultraviolet sterilization; The truth behind 11 common myths. Pet Age 8/93.

Escobal, P.R. 1991. The time required to sterilize a body of water with an ultraviolet sterilizer. FAMA 2/91.

Escobal, Pete. 1993. Inside ultraviolet sterilizers; determining the correct flow rate, power and diameter. Aquarium Fish Magazine 1/93.

Fenner, Robert. 1987, 88. Ultraviolet sterilizers use in filtration systems. Pets Supplies Marketing 6/88, FAMA 5/89.

Fujita, Grant 1987. Nishikigoi Book. Electrical Purification, p.107

Kennedy, Ron & Rosemay, 1986. Electronic U.V. Filter. In The Associated Koi Club's of America's, KOI BOOK, p. 85 & 86

Webb, R.B. & Brown, M.S., 1982. Genetic Damage in Escherichia coli K12 AB2480 by Broad Spectrum Near-Ultraviolet Radiation. Science, Vol 215, 19 Feb. 1982, AAAS