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Kevin L. Novak Ph.D. Ichthyology/Limnology Research    (R)

Are you thinking about building a garden pond or do you already have one? One of the main concerns of people building and/or already having a pond is the filtration system. Filtration is the most misunderstood part about pond keeping, but the most important part of a ponds ecological stability. Most people will look into a pond book, and build one that the book recommends or purchase one from a nursery center that sells pond supplies. The filtration methods and systems that are recommended in books, and there seems too be a plethora of them, and from nursery centers are usually too small and inadequate, with very old anachronistic technology. (This technology came from sewage treatment facilities back in the 1930’s). It was not until 1984 when George Smit, introduces a new type of filtration to the unfamiliar U.S. hobbyist. It is called the; “Dutch Reef Filtration System,” this system uses highly oxygenated filtration material, exposed to air and water, (it was coined the oxymoron: Wet-Dry Filtration Systems by the U.S. hobbyist.) In this method of filtering, water drips over the filter medium that could be plastic, stones and/or gravel or DLS material exposed to air. The bacteria from these particular filtration systems are able to break down ammonia 30 times faster than filtering material submerged under water. This particular type of filtration systems believed to be technologically superior in its ability of nitrification to the ones presently known at the time.

Nevertheless, there were some drawbacks to these filters; they produced more organic and inorganic compounds that added to the pollution and inorganic load (in the form of Nitrates) to the pond and/or fish tank. The bacteria have to secrete a polymeric type adhesive to protect them from water shear. This takes the bacteria on the filtration medium longer to establish itself especially if it were plastic. Unless there is an excellent pre-filter, the medium will begin to catch all kinds of organic matter and therefore will begin to clog; this organic matter can dislodge from the filter media and go back into bulk waters. Then there is the cost factor involved; it is their expense, for these filters are exceptionally expensive! It did not take the hobbyists long to find out what the downside of these particular filtration systems were (in the form of an overabundance of Nitrates).

Today many hobbyists obviously do not use these types of filtration systems, because they add to the DOC (dissolved organic compounds) and create large amounts of nitrogen. They are very inefficient at the using of phosphates. These types of filtration systems can add to the cyanobacteria¹ problem, which many hobbyist ponds are plagued with all the time. They also warp the ecology of the pond, which makes the ponds eutrophic in a very short time. Natural ponds approximately take from 100 to 1,000 years to age from a Ligotrophic state to a Eutrophic state. Eutrophication is nothing more than excess of nutrients in concentration. When organic matter and inorganic compound levels increase in a garden pond, sometimes it can become very visible to the pond owners, in the form of protein bubbles by a waterfall or unclear (turbid) pond waters. The turbidity of pond water begins to suffer, showing up as either green water or murky water, (a hazy murkiness look to the water, which makes the water look as if it has milk in it). The haziness is from complex organic substances like decomposing fish slime, urea, fish food, feces, dying algae, and metabolic by–products. Then add the phenols and many saprophytic bacteria that affect the fish growth rates, gills and weaken them, increasing their susceptibility to disease. These dissolved and suspended compounds makeup the biological oxygen demand (BOD), color, taste and turbidity of water. Biological oxygen demand is the amount of oxygen used by microbes, mainly bacteria, in the oxidation of organic and inorganic compounds.

Submerged filters are plagued with their own problems also. After initial start-up, they clog within 30 days (in order to stop clogging, it would require a 3 micron pre-filter) and you lose over 50 percent of available bacteria surface area. These filters are high producers of organic and inorganic compounds and are subject to organic clogging. When they begin to clog, (water will then seek the path of least resistance) these filters begin to harvest anaerobic areas. These anaerobic zones reduce nitrogen back into ammonia; this is called “Assimilatory Denitrification” ². They do not convert nitrates into nitrogen gas then release it into the atmosphere, as some hobbyists may think. Anaerobic heterotrophs reduce nitrates back to ammonia, and no further, period. They are very inefficient at the use of phosphorous for energy, resulting in abundant amounts of phosphates. The ammonia, which these bacteria make, is undetectable by hobbyist test kits. The fact is because of their inefficient use of phosphates, cyanobacteria can now take over, and it only takes 0.015 milligrams/liter to accelerate an alga spore into growing. The Merck Test Kits for phosphates will read below .015 mg/L, most hobbyist test kits will not test this low for phosphates. It is no wonder that when hobbyists do test for phosphates and their ponds are full of Blue-green algae that they cannot figure out why because their test kits are reading zero phosphates.

As you can see, making a filter work for us efficiently is no easy task. There are other filters out on the market but each one makes a by-product that another bacterium now has to breakdown into another by-product, and therefore adds to the organic and inorganic load. When the organic/inorganic load increases therefore redox potential decreases, one is in correlation with the other. The higher redox potential numbers correspond to oxidative states that are higher in value. Such values or states are, chemically speaking, only possible when no reductive processes are taking place. Reductive processes are those that are known as decomposition, decay, and so forth, and mean that pollution is present in the pond water. The lower the measured millivolt reading, the higher the pollution is present in the pond.

If these inefficient anaerobic bacteria produce more nitrogen-based by-products than can be used up by the efficient bacteria in areas that have aerobic bacteria and cannot be exported out of the pond then eventually the pond will have algae problems..

Some hobbyists will even go as far as making their whole pond into a huge filter, by placing rocks, gravel, and small stones on the bottom of their ponds. The same is true for what happens with this way of filtering, as with any other type. The stones will begin to clog, with smut, dead Algae, and detritus. Ammonium producing anaerobic bacteria will begin to leach ammonia upwards, algae then will use this, for this is a nutrient of prime importance, or it has to be converted back to nitrates by the aerobic nitrification bacteria. Nevertheless, as you can see, the pond will be plagued with the same problems as submergent filtration ponds have.

However, let us use this as an example, let us say you wanted to have a natural pond, and you wanted to cut out a section of 3,000 gallon from biotope in a forest preserve. You then cut out a section in this biotope and placed a liner underneath, and then had it dropped into a hole in your backyard. You would think you would have the perfect scenario! Unfortunately, you would not, because once you put the liner underneath this natural ecosystem you interfered with the intersection of topography, which ground water is going constantly into and out of the water body proper at the interface of the ground and water surface. The liner has cut off the movement of water through the soil substrate. The soil substrate/roots/water interface is of tremendous importance and is now disrupted by the liner. Natural ponds constantly have water moving in an out of them on a continuous basis. This is not just from the top to bottom movement but from horizontal and vertical directions. This would other wise be known as the “Z,” “X,” and “Y” movements of water through the substrate.

Unlike our ponds that are closed systems, natural ponds are open systems and are not plagued with the same problems, as our ponds. Therefore, with all that we know, how can we solve the problem of the filtration dilemma? The quest to solve, this one frustrating dilemma started me on a quest that took over sixteen years of research. The answer is not a simple one, and a great amount of scientific experimentation played a big part in solving this problem. Is this the Holy Grail of pond filtration? Maybe not, but it is as close to it with what is known today.

As the old saying goes, “If you build a better mouse trap people will buy it.” First biophysical rules for this kind of filtration are different from that of filtration systems most hobbyists use in their ponds today. In hobbyist filtration systems, the overall efficiency of the filter is in relation to the filter’s-incoming foodstuff. Nutrients flux of incoming nitrogen reacts differently to levels of nitrates in the system that is if microbial mediators are in equilibrium with each other. If excess occurs, there may be a lack of balance and/or useful microbial mediators. This will occur when clogging of the filter medium is present or oxygen concentrations are high in bulk water. The filter bed having more anoxic³ and less anaerobic volume area where more efficient facultative anaerobic exist will be able to respond extemporaneously to the nutrients flux more efficiently. The fact is that when glucose is randomly added to these facultative anaerobes they have an Adenosine Triphosphate (ATP) yield of approximately 34 times that of anaerobic heterotrophs. Adenosine Triphosphates correspond to the speed and efficiency nutrients can be reduced to make energy. Organic carbons do not limit these bacteria and mineral nutrients as heterotrophic bacteria do, which will have a negative impact on other chemolithotropic processes.

With the Anoxic Filtration System, biochemical pathways are always open and never clog. The oxic–anoxic interface microbial processing is the principal processing, controlling electrons flowing from organic matter to oxygen in molecular diffusion. This filter also has a diffusion of nutrients through it influenced by electrical charge⁴. The filter biocenosis-baskets are negative mV. Moreover, in the pond are many charged molecules, which mostly are positive mV. The more positive nutrients are naturally attracted to the filter biocenosis-baskets that are then used by facultative anaerobes. These bacteria are thirty times more efficient than bacteria in oxygen free zones, make better use of phosphorus and only trace amounts of phosphates. Reducing nitrates back into gas elements, (Dinitrogen (N₂) is called Dissimulative Denitrification⁵. Illustration #1 shows how the charged molecules are in relationship to the bulk waters.

Illustration 1: Showing the negative and positive charges of the bulk-water and basket.

Making up biocenosis-pots for filtration and plants is really quite simple. The supplies you will need are large planting baskets (11" x 11" x 7" or 14" x 14" x 10"), kitty litter 10 (with no additives just plain clay), and Laterite that will be for the substrate. Laterite is a highly weathered remnant of volcanic rock (weathering implies exposure to tropical temperatures, precipitation, and forest derived humic acids over geologic time). Very rich in iron, and Manganese (iron is needed for plants to make chlorophyll). Taking a plant basket as shown in illustration #1 then filling it with Kitty litter, make sure you leave a small impression in the center of the basket. Take about one cup for smaller baskets and one and a half cups for larger baskets of Laterite and pouring it into the center of the basket then mixing the Kitty litter and the Laterite in the center of the basket. Now place only one layer of pond pebbles on top, this is to keep the Kitty litter from floating up after submerging it into the pond. Instead of using pond pebbles, you can also use a black craft screen on top and wire-tie it to the basket. The Laterite will help the bacteria grow in its early stages, once the bacteria becomes established, it will be less dependent upon the iron in the Laterite for growth. The good thing about the planted basket is it will take years before clogging with organic matter (it may take 18 years or longer). You will use the same procedure for the planted biocenosis-baskets, but you will not use the black craft screen on top of this basket only the pond pebbles.

If you were wondering why you did not use any nitrogen tablets in the basket, it is because plants must get their nitrates into their cells against an electrical gradient. Plants, algae, and all photosynthesizing organisms use the N (NH₃ and NH₄+) of ammonium, not nitrates, to produce their proteins. Using nitrates is costly to the plant in terms of both electrons (e-) and energy. Because NH₃ is a small molecule (NH₃ ammonia enters plants even more easily than NH₄+ ammonium) without an electrical charge, it freely diffuses back and forth across the cell membrane barrier. The energy required is so substantial for the plant that nitrates are only taken up in the daylight (during photosynthesis) whereas considerable ammonium uptake will continue in the dark, all night long, long after photosynthesis has stopped. The fact is that pond plants do not begin the process of photosynthesis, until the sun begins to rise. However, it is not unusual for plants to begin photosynthesis until as late as 11:00 a.m. only for this process to peak around 2:00 p.m. in the afternoon, then slow down at sunset. After the process of photosynthesis can no longer take place, the plants will begin to generate carbon dioxide instead of oxygen. The plants do not have as much time to deal with excessive nitrates in solution, as you would think.

The energy used represents about one-fourth of the energy required for the plant to produce its carbohydrates. Photosynthesis is reduced by one-third in the conversion of each Nitrate to ammonium, in a two-step process of Nitrate reduction; the plant for increase growth and flowering could use this energy. The fact is none of our aquatic plants need nitrates as a food source, only ammonium, and there are only a few exceptions to this rule, one is Eichornia Crassipes (Water Hyacinth), with 75 percent of its food source being nitrogen and 25 percent being ammonium. Aquatic plants potted in compost, humus or topsoil endowed with organic matter will certainly grow luxuriantly. However, excess nutrients that leak into solution from such media will lead to the eutrophication of the garden pond. This state of affairs arises from an over supply of plant nutrients in solution that favors the growth of algae at the expense of vascular plants.

Laterite or clay (Kitty litter) has a crystalline structure attracting cations (positive ions like k+, Ca+++, Mg++, Al+++). If other growth factors are present in reasonable amounts, (Note; this is called the Liebig Minimum Law⁶) you will have good root growth.

By good root growth, we do not mean many roots. You can have hardy plants with big, thick masses of roots in other systems. What we mean here is root hairs in proliferation filling up a planted pot. The more proliferation of root hairs, the better the plants uptake of cations and anions out of the water body proper. The adsorption and absorption, or in equal equilibrium between anions and cations is very important. If anions where taken into a plant without cations in equivalence, any plant would suffer from a fatal pH swing. Repeatedly it has been observed that the uptake of nitrates from pond containing both ammonium and nitrates only starts after ammonium has been exhausted or its concentrations greatly reduced.

Building the filter that holds the plants is not rocket science. The first thing you have to do when building the filter, which can be any size or shape you wish it to be as long as its capable of holding all the filter biocenosis-pots on the bottom. Remember, that it must be at least 24 inches deep; this will ensure that there will be at least two cubic feet of water (15 US gallons) for every square foot of pond surface area. Experience shows this offers more stable water conditions and makes control of suspended algae somewhat easier.

The minimum number of biocenosis-pots for a small pond would be 15 biocenosis-pots and at least five of those would be planted with plants in them. Of course if you wish to pot up all 15 biocenosis-pots with plants you can, this will only add to the filtration system. Another good thing about this filter is the flow rate of water through it. The faster you can get water from point A to point B the better the filter actually works. You see this filter is not dependent on the flow of water through the filtering material. Most filters made are dependent on how much water at a given rate can be flowed through them. If the water flows too fast, the filter will not work correctly. This does not mean that the bacteria will die but its efficiency will diminish greatly because of the bacteria’s ability to resist water shear will be lessened to a greater degree than if the flow was at the correct rate. If water flows too slowly, the filter will become inefficient at breaking down waste products, because the bacteria need so much oxygen to carry out the biological process. In this filter, water is not forced through the substrate, but a slow, steady, diffusion and/or convective; movement is achieved through the substrate. Most hobbyists who build these particular filters find out that they are buying new pumps that actually pump more gallons per hour than their old pond pumps did, because this filter will perform at its best with faster flow rates.

Photo 1: Shows finished Anoxic Filtration System (R) with 22 biocenosis-baskets, only ten-baskets have water lilies in them. Also shown with water-outlet-diffusion system.

The only downside of pumping so much water through the filter is that it is imperative to diffuse the water in the main filtering pond. This is because you do not want the water stirring up any organic matter, inside the filtering area. The filter actually acts as a big settlement chamber that allows any smuts, detritus, or dead algae to be collected in it, that the pre-filter or skimmer does not get before entering the filtering pond. So diffusing the pumps out-put is of the highest priority when using this type of filtration. Illustration #2 shows such a diffusion system; as an engineer/scientist, I designed this diffusion system so that it can diffuse over 6,000 gallons per hour. The system works so well that it will look as though hardly any water is entering in the filtering area. This diffusion system is quite easy to make, as the illustration is self-explanatory on how to make it, but this is not the only way or means of diffusing the incoming water. Some hobbyists who make their own homemade systems have executed some very ingenious diffusion systems. The good thing about the diffusion system that I have designed is that it will only takes up one square foot of the filtering area, is extremely easy to clean, and will last almost indefinitely.

Illustration 2: Shows the diffusion systems logistics. However, this is not to say, this is the only way to diffuse the incoming water.

The very low to almost non-existing maintenance on this filter makes it a very big plus for any pond owner. Cleaning will only take place twice a year, once in early spring and another time in late, fall and you do not have to remove any of the biocenosis-pots during the cleaning process. It is also not electrical dependent, which means that if the power should go out for hours, or even days, the filter would not be affected in the least bit. For the chemolithotrophic, bacteria and the facultative anaerobic bacteria would continue to function without the water movement through the filter. Another plus is its ability for the facultative anaerobes to behave as respiratory heterotrophs when nitrates are exhausted.

Research has shown that even the type of pots and baskets that are used play a very important part in this filtration system. One of several experiments that were conducted, was to take two different kinds of plant containers, one was a pot you may get at any nursery center with holes only at the bottom of it; the other was the open-cell-plant basket. The pots and baskets where planted up with Acorus Calamus (Sweet Flag). Kitty litter and Laterite were both used as a substrate. The pots and baskets were then submerged into a pond with an oxygen content of no less than 8mg/l. There was to be a grow-out period of four weeks for the plants to become established. After four weeks, the pots and baskets were to be removed from the experimental pond for examination, for their oxygen content, plant growth, root development, and bacteria growth. It was discovered that the pots that only had the holes at the bottom of them already smelled like hydrogen sulfide⁷. Assimilatory Denitrification by sulfate reducing bacteria and methanogenic bacteria were present, oxygen levels were between .5mg/l- 0mg/l as tested. The open-cell baskets smelled sweet⁸, meaning that there was still oxygen but at low levels (between 1.8mg/l-.5mg/l). The plants in the open-cell baskets were already showing good root growth. The plants in the pots that only had holes at the bottom of them showed very little to no root growth at the time.

Nature’s way of diffusion, moving of molecules from one place to another, is the way that nature moves solutes in fluids. It seems apparent that this fundamental process of transporting molecules from solution through the substrate is disruptive with the pots that only had holes at the bottom of them. In the early stages of plant growth, convective movement of fluids is not dependable and the substrate will become anaerobic before it will become anoxic in nature. As healthy root, growth becomes apparent then the substrate will become less anaerobic and more anoxic in nature. The open-cell-baskets allow diffusion to take place over convection and therefore allowing more nutrients and oxygen in solution to be transported more easily through the substrate. Once the plant roots became more prolific, a steady, slow, convective movement through the pot substrate became apparent and oxygen levels became satisfactory for anoxic condition to exist.

The degree of filter permeability is what changes its biophysical rules on which filter media is used. In a close system like or ponds, the microbial efficiency is in relationship to the media and/or substrate and incoming foodstuff that is of great importance. As long as the pathway remains open to the microbial mediators, equilibrium will exist between the aquatic life and bacteria. But because of clogging these nitrogen pathways become blocked affecting and limiting the organic carbons, this is known as the Redfield Ratio and contributing to algae blooms, hair and string algae problems. Clogging is not an issue with the Anoxic Filtration System and therefore all pathways remain open. Therefore, organic carbons and mineral nutrients do not limit heterotrophic bacteria.

If you have learned anything from this article, it is that biochemical pathways always remain open to the bacteria, versus other filtering systems pathways. The plants will proliferate, adsorbing more cations and anions (anions equal nutrients like nitrates and phosphate) than other ways of planting. Maintenance compared to other filtration systems will be exponentially lessened to a greater degree.

If you already have an existing filtration system, it is not to be integrated with this type of filtration. One system will be counterproductive to the other filtration system (Note: that is if the system you are using at present is not of high standards. Some filtration systems are so inadequate and mis-engineered, that the hobbyist is doomed from the start.) and you will never have complete success. It does not take a large filter to make it a successful one; a 4’x 8’ filter will hold as many as 28 filtering biocenosis-baskets. That is enough biocenosis-baskets to filter a 8,000 gallon pond depending on the fish load.

As I write this, I realize this topic is like discussing politics or religion. Strong misconceptions and beliefs die very hard. Most of the time, we just go on believing in our own doctrines and others keep believe in theirs. With this filtration system its primary path of biological pathways are from diffusion⁹. This system plays an integrated part of the biological capability of nitrifying-denitrifying a pond and its capability of purifying it for aquatic life. Its oxygen demand on the aquatic animals in our ponds is not demanding, and lessening the burden of the consumption of oxygen, means healthier fish in the summertime.

However, if you find you are interested in such a filtration system, you can contact me, and I can explain further any misconceptions that you may have and/or you can also read my informative Q&A, which will shed some light on this subject to a greater extent. At the end of this article, I will show you other people’s ponds that have such a filtration system and their success that comes from having one. My pond is over 18 years old now, the Koi in it are as old, and most are older. A Beta-testing pond that conducts experiments for me is over 15 years old and its Koi are as old as the pond. All consultations are free; I do this for the betterment and education of the hobbyist, not for monetary value.

Illustration 3: Top view of Anoxic Filtration System integrated with Koi pond.

Graphic Designs By:

Kevin L. Novak

All rights reserved.

No part of this article may be reprinted in any form without prior written consent from the author.

Printed in the USA.  Copyright 2005(C)    Patent pending     Anoxic Filtration System(R)™

Footnotes

• 1. Cyanobacterium is the group of photosynthetic bacteria that have two photosystems, that produce molecular oxygen, and uses water as an electron - donating substrate and photosynthesis - also know as string algae, hair algae, and blue – green alga.
• 2. Assimilatory denitrification occurs in anaerobic areas were nitrates are reduced to ammonium (NH₄+). Obligate anaerobic heterotrophs accomplished this in oxygen free zones, when exposed to oxygen die very quickly. This is known as “Ammonification,” a form of denitrification.
• 3. Anoxic is a more recognized word than the unfamiliar words “dysaerobic” or the medical term “hypoxic” to represent areas in the substrate where very little oxygen is present. This way of filtering contains approximately 2.0 mg/L to .5 mg/L of oxygen and is where destructive denitrification takes place.
• 4. The clay (Kitty litter) and Laterite itself are negatively charged and increasing magnitude with depth. The deeper the plant basket, the more negatively charged it becomes and the more positive charged nutrients are naturally attracted deep inside the biocenosis-baskets.
• 5. Dissimilatory denitrification is accomplished by facultative anaerobic heterotrophs and lives in anoxic zones.
• 6. The Liebig Minimum Law is that plant growth is determined by the one factor that is present at a minimum. That is healthy plants must have all nutrients in the correct proportions. The first five major elements are sunlight, CO₂, Iron, Manganese, and Ammonium (NH₄+). The law also holds true for trace elements as well.
• 7. Hydrogen Sulfide is a poisonous gas (H₂S) that has an odor of rotten eggs.
• 8. Sweet smell; means that the clay biocenosis-baskets had no other odor than that of the ponds natural smells.
• 9. The process whereby particles of liquids intermingle as the result of their spontaneous movement caused by thermal agitation and in dissolved substances move from a region of higher to one of lower concentration. Diffusion is fundamental way molecules collide and react; how food molecules approach cells, and how waste leaves local environments. That dynamic process that helps many biological functions takes place, and physical factors take place. Diffusion is a part of all ponds whether natural or fabricated, diffusion will exist to one degree or another in all systems.
• 10. Kitty litter and/or cat litter is not really a potting medium, but it works very well as one. Kitty litter made from calcified clay (which is mined from the earth, cleaned, baked, and pulverized) is best because it has not been chemically treated or deodorized. Avoid products that contain anything with non clay materials in them. Kitty litter is as good as clay soil at holding nutrients, yet it will not muddy pond water if disturbed. It will not float or clump.

THE PHOTOS ON THE NEXT PAGES ARE SOME OF THE PONDS
THAT USE THE ANOXIC FILTRATION SYSTEM.

Photographs by the author unless otherwise stated.

More photos of people using the Anoxic Filtration System can be found on http://happywaters.org
Go to Photo Gallery, then 2007 Happy Waters Pond walk.

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