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8.9.1. Biocenosis Reactor

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Author : David Bogert

Published :

Time To Read :
35 minutes

“Biocenosis reactors”, “biocenosis clarification baskets”, “BCBs”, and “anoxic plenums” are devices which are claimed by a Dr. Kevin Novak to remove nitrogen from an aquarium by converting ammonia to nitrogen gas in anoxic conditions. The Biocenosis Clarification Basket reactors are simply mixtures of kitty litter and laterite gravel placed either in a porous plastic basket in a sump, trays in a canister filter or as gravel in an under-gravel filter (a “plenum”). 

Dr. Novak has a YouTube channel where he continually advocates these baskets and plenums. These YouTube videos are just … well … er  ….. strange!  The “science” expounded in these videos, while apparently sincere, is simply wrong. Sorry, I just can’t sugar coat it.

In a nutshell, the kitty litter/laterite devices do not work. Year long side by side testing with controls proved they do not work. There are no less than six separate solid scientific requirements for any anoxic denitrification device to work. The biocenosis baskets and anoxic plenums meet NONE of the six requirements. NONE!

BCB Basket
BCB Basket

There are several YouTube videos and a blog which claim successful removal of ammonia or nitrates from an aquarium via reduction to nitrogen gas using a biocenosis basket or an anoxic plenum. All these aquariums or ponds had large accumulations of plants or detritus which clearly absorbed the ammonia or the nitrates into their mass as proteins. There were never anywhere near “anoxic” or “anaerobic” or even “hypoxic” conditions created in ANY of these aquariums. And no nitrogen gas ever gassed off from these aquariums or ponds.

Also the science behind anoxic denitrification of nitrate to nitrogen gas dictates that biocenosis clarification baskets and plenums simply cannot work. If one needs more details, wants to be bored to death by a lengthy, verbose analysis designed to prove a negative, and is a real nerd like the author, read on.

Pterophyllum Scalare Blue Avatar Angelfish
Pterophyllum Scalare Blue Avatar Angelfish

A Predicate Statement 

The whole topic of biocenosis baskets and anoxic plenums is just … well … strange. To illustrate this “strangeness” there seems to be an issue which needs to be aired prior to anything else. In a video on Dr. Novak’s YouTube channel there was an interesting exchange in the comments section between one Bentley Pascoe and Dr. Novak. Mr. Pascoe said he was data oriented researcher and needed to see the research and the data on the Anoxic Filtration System. Dr. Novak then commented as follows:

“Since the anoxic filter has been out to the public for over 30 years now and has been tested all over the world: now 30 years later you come up and ask for actual data that you would like for FREE? Tests, articles, and books have been written about Anoxic filtration system for the past 30 years: where have you been? However, if you would like to have all my research papers then contact me and I will tell you the price that I’m selling them for.  That’s if you would like to buy them, after all research is not free and since I do not know you, you could be working with a company.  I don’t hand over 10 years of research for absolutely free. So if you really are that interested, then you contact me, and I will tell you the price of all the research papers and then you can have them after payment. I’m no different than anybody else.  I want to be paid for my services and time just like you do with your YouTube channel, you want to be paid for your services and time; you put a lot of effort into what you do, so do I.”

Dr. Novak
Cyphotilapia frontosa
Cyphotilapia frontosa

So I left a comment on the YouTube channel (and sent an email directly to Dr. Novak) that said:

“You say, and I quote: “Tests, articles and books have been written about Anoxic filtration system for the past 30 years” but that you want to be paid to provide this literature. Fair enough. I’ll purchase a copy of this literature. Please tell me the price and how I can obtain a copy of it. Thank you, David Bogert”

Dr. Novak came back with the following:

“The research papers that I have, and everything is for sale for 1.5 million. You come up with the money I’ll come up with the papers. I have lots of people I can pay with that money who help me do the research.”

This is just … well … er  ….. strange!  Draw your own conclusions. I won’t speculate.

Retroculus xinguensis
Retroculus xinguensis

“Biocenosis Clarification Basket” and “Anoxic Filtration”

Note there is one “anoxic/aerobic denitrifying system” for aquariums on YouTube which is just … well … er  ….. strange!  It is a “Biocenosis Clarification Basket” (and its similar “anoxic plenums”). These videos are simply a bunch of rambling statements using some big terms that make no coherent scientific sense at all.

The author, Dr Kevin Novak, seems very sincere and appears to have very good intentions. He seems to be genuinely trying to help out the hobby. Dr. Novak just seems to have the science all jumbled up and inside out.

Dr Novak says that his aquariums are without nitrates after eight months without doing a water change. And he ascribes this to his filter removing the ammonia and/or nitrates by “biocenosis” by an “anoxic filter” that converts nitrates to harmless nitrogen gas.  Here is a photo of one of Dr. Novak’s “zero nitrate” anoxic plenum aquariums. Note all the fast growing plants and the low number of fish:

6/6/2022 "Result" of an Anoxic Plenum
6/6/2022 “Result” of an Anoxic Plenum

Dr. Novak has several heavily planted, lightly stocked aquariums which are simply low tech heavily planted aquariums! And plants absorb ammonia and nitrates! If the fish loading is low, the plants can keep nitrates at zero. “Biocenosis” is a term which means “an association of different organisms forming a closely integrated community”. I.e. a low tech planted aquarium. This is a photo of another of Dr. Novak’s aquariums:

Dr. Novak's Aquarium with biocenosis basket
Dr. Novak’s Aquarium with biocenosis basket

The large volume of plants in these lightly stocked aquariums will reduce the nitrates to zero. This is not the “biocenosis reactor” or the “anoxic plenum” doing the reduction. 

Dr Novak also showed some pictures of his koi pond where he claimed nitrate reduction by use of a biocenosis basket. It was filled with emergent vegetation. Emergent vegetation is a well known absorber of nitrates. EVERYONE knows that!

But Dr. Novak has a video where he says plants are NOT needed for the biocenosis reactors to reduce nitrates. Could he possibly be referring to absorption of nitrogen by the proteins in living organisms in biofloc? But, no, he continually states the nitrogen goes to gaseous nitrogen in his baskets and plenums.  This is just  … well …. er… strange.

Dr. Novac's Pond with "Anoxic Filtration"
Dr. Novac’s Pond with “Anoxic Filtration”

The Strange Terminology

These “biocenosis baskets” and “anoxic plenum” YouTube videos use some … well …. er… strange terminology like:

  • Clay attracts ammonia” (when water with ammonia in it flows directly and microscopically [like the diameter of an atom microscopic!] onto the surface of a UNFUSED clay particle the positively charged ammonium ions can be exchanged for positively charged sodium or calcium ions on the surface of the clay. The clay does not “attract” anything. And FUSED clay such as kitty litter doesn’t even do the exchange of positive ions that UNFUSED clay can do)
  • The electrical charges in the center of the basket only draw in ammonia molecules; they don’t draw in water molecules“. (There is no “electrical charge” in the center of any basket of kitty litter and/or laterite. If there was a negative lead from a DC power source in the center of the basket and the positive lead from the DC were placed in the water outside the basket, positive ammonium ions [and all sorts of other positive ions] would be drawn into the basket. But there is no DC source. There are no electrical wires giving some “charge” to the center of the basket.)
  • Fused clay has a glass structure and is thus crystalline” (glass structures are amorphous, exactly the opposite of crystalline)
Aulonocara baenschi Sunshine Peacock
Aulonocara baenschi Sunshine Peacock
  • Oxic/anoxic denitrification” (an impossibility as oxic [oxygen rich] and anoxic [no oxygen] conditions cannot exist in the same media)
  • Negatively charged cat litter” (there exists no such cat litter or no such material, all the negative charges in any clay particle have positive ions attached to them so there is no net charge. And as a FUSED material, kitty litter has no charges at all)
  • Positively charged ions/molecules dominate bulk waters.”  (Every single positive ion in water has a corresponding negative ion for no net charge. And “dominate bulk waters”? What does that even mean?)
  • 220 molecules of NH₄ become 216 molecules of NO₃” (now this process is destroying atoms of nitrogen).
Dragon Blood Peacock Cichlid
Dragon Blood Peacock Cichlid
  • kitty litter that has a crystallinity that attracts ions” (kitty litter has no crystallinity, it is FUSED clay and as such it is amorphous. In any case crystallinity does not “attract ions”)
  • Negatively charged sites in the clay dominate each filter basket and attract positive ions” (Each negatively charged site in any clay has a positive ion attached to it for no net charge. And FUSED clay, like kitty litter and laterite, has NO negative charged sites. And there is that “dominate” word again. Dominate means “most important, powerful, or influential”…  hmmmm  …. what does this even mean?)
  • Current carrying magnetic field” (there no such thing in the absence of an electric current in the aquarium! Even an electric current flow will not produce anything “magnetic” in water)
  • “Anoxic bacteria metabolize ammonia to nitrogen gas to provide their energy needs” (just simply completely impossible and untrue. Bacteria which reduce nitrate to nitrogen gas require a lot of energy from other sources in order to accomplish denitrification. And there is no organism which converts ammonia directly to nitrogen gas under ANY set of conditions). 
Protomelas taeniolatius Boadzula Red Empress
Protomelas taeniolatius Boadzula Red Empress
  • Magnetic permeability” (there is no “magnetic permeability” in aquariums, it applies in the design of electrical motors, not in an aqueous solution)
  • Positively charged aquarium water” (again, no such entity exists. In all water the number of positive ions is EXACTLY the same as the number of negative ions)
  • Magnetic dominant ions are positive ions” (which is quite simply just gibberish which uses scientific words. There is no such thing as “magnetic dominant ions”).
  • You need the laterite for the iron” (laterite is a common rock which is colored red by iron rust. Iron rust is a mixture of iron oxides and hydroxides from which bacteria or anything else cannot remove iron from because it is too tightly held. The red laterite soil in Hawaii which grew pineapples needed iron supplements because the pineapples could not pull the iron out of the laterite)
Labeotropheus trewavasae Thumbi west
Labeotropheus trewavasae Thumbi West
  • Bacteria when it is new needs a lot of iron” (bacteria is NEVER “new” or “old” it simply splits in two to multiply so there is no such thing as “new” or “old”. And the amount of iron needed by all bacteria is incredibly tiny [iron isn’t called a “micro-nutrient” for nothing], rather obviously since bacteria can grow almost anywhere).
  • The bacteria steal the oxygen from phosphates” (take it from a chemist, nothing will “steal the oxygen from phosphates”. To do that one is reducing the phosphate to phosphorus, something which is completely and totally impossible in an aquarium)
  • Microscopic thermodynamics” (“thermodynamics” is the study of heat flows. Any biofilm will be a very uniform temperature and have absolutely no heat flows, microscopic or otherwise)

Not one phrase in this list of eighteen makes any sense at all. This is just … well … er  ….. strange!

Heros severus cf. efasciatus Rotkeil Severum
Heros severus cf. efasciatus Rotkeil Severum

Dr. Novak has a book available over Apple I tunes which basically simply repeats the above … well …. er… strange ideas over and over again. Typical of these strange ideas is this paragraph from Dr. Novak:

“The anoxic filtration acts like a natural system by allowing ions to flow freely into and out of the substrate. This keeps the basket in an aerobic state also in an anoxic state but not an anaerobic state. And natural systems works the exact same way where ions are allowed to travel into and out of the substrate through the intersection of typography. If this movement is hindered in anyway that then changes and/or upsets the bacteria balance to available food stuff in the system and the system then can in some cases becomes an Ethiopian system and will affect microbial cells and life in the system.”

Dr. Novak

“Aerobic state also in an anoxic state?”, “intersection of typography?”, “an Ethiopian system?” Once again, a bunch of terms which just do not make any coherent sense at all. Not one sentence in this paragraph makes any sense at all. This is just … well … er  ….. strange!

Theraps Bocourti
Theraps Bocourti

Another write up of Dr. Novak is:

“Anoxic Filtration System: Is a biological filtration system using Biocenosis Clarification Baskets to attract positive ions out of the water body. Using a combination of natural process clays, like that of Kitty/cat litter and tropical Laterite, a residual product of rock decay, act and react to convection, magnetic pull and/or diffusion as a biochemical reaction to attract cantons and anions out of the water column. Because of their crystalline structural state, the negative charged clay read in mV, (electrovalence) attracts positive ions like ammonium and removes it out of the bulk water. This magnetic pull will them aid in molecular diffusion, using Facultative anaerobic hydrotropic bacteria, therefore creating under anoxic condition Dissimulative Denitrification and will turn Nitrates NO₃ into Dinitrogen Gas (N2). Thus making it safe for aquatic life to exist in ponds.”

Dr. Novak

ahhh… eeer…hmmm ….. ??? This is just a whole series of disjointed non sequiturs (a conclusion or statement that does not logically follow from the previous argument or statement) that sound very scientific with big words which again make no coherent sense. Once again, not a single sentence here makes any sense. This is just … well … er  ….. strange!

Protomelas sp. spilonotus Tanzania
Protomelas sp. spilonotus Tanzania

Then there is a whole group of koi folks in the United Kingdom that somehow believe in these “biocenosis baskets” in kind of a club. One member who writes some articles on it is Syd Mitchell. Some of this club ascribe the nitrate removal to plants while Dr. Novak steadfastly insists plants are NOT part of the equation and that everything ends up as nitrogen gas via anoxic bacteria. This group even has a course one can buy for $50 on “Anoxic Filtration 311”.

Manke Sanke is a UK koi pond website with an article on the biocenosis baskets. This article used a lot of the “strange” terms listed above. After this article came out it was rewritten to eliminate the “strange” terminology and to simply claim the baskets attract ammonia and that anoxic bacteria then convert the ammonia to nitrogen gas. It was still categorically wrong. Anoxic bacteria cannot use ammonia as source of nitrogen gas.

The Biocenosis Clarification Basket reactors are simply mixtures of kitty litter and laterite gravel placed either in a porous plastic basket in a sump, trays in a canister filter or as gravel in an under-gravel filter (a “plenum”). To claim that an open gravel sized media such as this will produce anoxic conditions simply cannot be supported by science. Can’t even happen in a fine substrate, let alone a substrate as open as kitty litter. 

For information on the science of anoxic denitrification in a substrate click on the following link:

14.2.4. Anaerobic Substrates

picture of an aquarium fish Placidochromis Phenochilus Madoka “White Lip “
Placidochromis Phenochilus Madoka “White Lip “

What is Kitty Litter and Laterite?

Kitty litter is clay which has the following done to it:

  • The UNFUSED clay is dug up from deposits in Georgia or Florida
  • The UNFUSED clay is loaded onto conveyor belts and spilled into giant crushers. The crushers break the UNFUSED clay into smaller pieces, then deposit them onto another conveyor belt, which feeds the clay into a kiln.
  • The kiln resembles a horizontal chimney or sewer pipe, 30 m. (100 feet) or more in length. Inside the kiln, where temperatures can reach 1093°C (2000°F), lifters tumble the clay as it bakes. The clay continues its baking process until it has traveled the entire length of the kiln and become FUSED clay.
  • As the FUSED clay emerges from the kiln, it is fed into a second crusher. Here, rollers crumble the FUSED clay to its final consistency.

What is VERY important here is the word “FUSED”.  FUSED ceramics are INERT ceramics. INERT means they don’t “DO” much of anything. FUSED porous clay (i.e.  kitty litter) does not have any negative charges associated with it in any way. FUSED porous clay does have an ability to absorb an amount of liquid equal to its own weight. But that is the ONLY useful property it has.

Hard laterite gravel is basically just porous FUSED clay with iron oxides in it, i.e. virtually identical in its properties to kitty litter. Sometimes laterite is produced by man from iron rich clay, sometimes laterite is weathered volcanic rock produced by nature.

Amphilophus citrinellus Midas cichlid
Amphilophus citrinellus Midas cichlid

The Structure of Clay and Laterite

UNFUSED clay has a structure which is a stack of very thin sheets with a water/salt solution in between the sheets. The silicates in the UNFUSED clay have little “knobs” that stick out into the water film sandwiched between the clay sheets on an incredibly tiny atomic scale.  The knobs have an incredibly tiny negative charge to them. So in  UNFUSED clay, on each knob, there will be a positive ion (i.e. a “cation”) VERY lightly attached, like iron (Fe), potassium (K) or calcium (Ca) cations, along with water.

The structure of hydrated clay
The structure of hydrated clay

UNFUSED clay is a material which has something called a high “cation exchange capability”. This means it can exchange one positive ion for another positive ion in a water solution. So it can exchange, i.e. “release” a positive calcium ion and “grab” a positive potassium or ammonium ion.

Aulonocara maylandi Sulfurhead Peacock Phoenix
Aulonocara maylandi Sulfurhead Peacock Phoenix

If the UNFUSED clay has 95% calcium and 5% potassium ions in its lattice and the surrounding water has 75% calcium, 8% potassium and 17% ammonium in the water, the UNFUSED clay lattice will slowly “exchange” to an equilibrium point which is 75% calcium, 8% potassium and 17% ammonium. The UNFUSED clay particle will then simply “store” the excess potassium and ammonium till the water composition changes.

“Exchange” and “attract” are two completely different things. Each negatively charged site on a clay particle will have a positively charged ion attached to it. So there is no net “attracting” negative charge possible. The clay as a whole does not have electric charge, the negative charges of the clay particles are balanced by the positive charge of the cations in the clay.

But in any case the whole discussion becomes very pointless when one considers that kitty litter is FUSED clay.  When clay is fused the water between the sheets of clay is driven out. This fuses the sheets. There is no way to reintroduce the various cations and the water once this is done. So FUSED clay (i.e. kitty litter) has zero cation exchange capacity and absolutely NO NEGATIVE CHARGE of ANY sort, tiny or strong.

Labeotropheus fuelleborni Chimwalani
Labeotropheus fuelleborni Chimwalani

And So What?

And say the fused clay did somehow attract ammonium ions and allow them to attach to the clay particles. So what?

  • Anoxic bacteria do NOT use ammonium ions to produce nitrogen gas.
  • Anoxic bacteria reduce NITRATE to nitrogen gas using a carbohydrate as an energy source and nitrate as an oxygen source.
  • Clay particles do not reduce nitrate, ammonia or ammonium to nitrogen gas.
  • If kitty litter did somehow have a net negative charge (it doesn’t) it would repel nitrate, a negatively charged ion.
  • Since the clay particles do NOT have a net negative charge they cannot attract and concentrate the ammonium ions.
  • Iron oxides do absolutely nothing for the process. NOTHING!

I.e. the even actual unfused clay particles could do absolutely nothing for these anoxic bacteria for a whole host of reasons. NOTHING!  There is no connection between anoxic bacteria and clay ion exchange or iron oxides.

The design of this “Biocenosis” reactor put forth in this video will not even come close to producing the conditions required to reduce nitrate to nitrogen gas.  And Dr. Novak never makes any statement I heard which makes any scientific sense at all. The many profit oriented charlatans on YouTube mix accurate science with their concocted science. And most YouTube charlatans are selling a product. Dr. Novak doesn’t do that. So I have no idea what is going on in these YouTube videos. This is just … well … er  ….. strange!

Champsochromis caeruleus Malawi Trout
Champsochromis caeruleus Malawi Trout

Note Dr. Novak has a whole series of videos where he converts undergravel filters to “slow flow anoxic filters” or “plenums”. All these videos are also …. well … er …. strange. All these designs have all the scientifically incorrect claims of the “biocenosis baskets” and all simply won’t work. Anoxic reduction of nitrates to nitrogen gas will NOT occur with any of these designs. And aerobic oxidation of ammonia to nitrite will be very poor with these designs as decent flow rates are required for efficient aerobic oxidation.

Dr. Novak came out with a video where, after six months, his aquarium with a anoxic plenum was up and “operating fine”. He then says in the video he is changing 50% of the water every four weeks to keep nitrates down. Huh? I’m confused!  And the point of the anoxic plenum is? This is just … well … er  ….. strange!

Biotodoma cupido
Biotodoma cupido

Experiment with Clay and a Battery

Dr. Novak referenced one video where a slurry of montmorillonite clay is charged by a battery. The clay forms a solid ball around the positive wire and no ball around the negative wire. The presenter says that the clay does this because it has a negative charge and is being attracted to the positive electrode. Dr Novak says this explains why positively charged ammonium cations are attracted by clay.

In the experiment the clay particles are NOT being attracted to the positive terminal. Rather the interstitial positively charged cations and associated water molecules are being attracted to the negative terminal. A reference is in order:

“Electro-osmosis is an established method of expediting consolidation of soft, saturated clayey soils. In electro-osmotic consolidation a direct current (DC) is applied via inserted electrodes. This causes hydrated ions in the interstitial fluid to migrate to oppositely charged electrodes. Because the clay particles have a negative surface charge, the majority of ions in the interstitial fluid are positively charged. Therefore, the net flow of water will be towards the negatively charged electrode (cathode), where the water can be removed and thus consolidation is achieved at the positively charge electrode.”

“Effects of Electro-osmotic Consolidation of Clays”, Lucas Martin, 2019

What is happening here is that the negative current flow is depleting the clay particles at the positive terminal of positive charge cations and their associated water (see the diagram of a hydrated clay particle above), drying out these particles. This drying action causes the clay particles to stick to each other in a solid mass around the positive terminal.

The clay is NOT being attracted to the positive terminal. The trapped cations and their associated water are being attracted to the negative terminal over a considerable distance by a current flow in form of positively charged ions.

Chilotilapia rhoadesii
Chilotilapia rhoadesii

The proper way to have done this test would be to add a small amount of montmorillonite clay to water to make a cloudy suspension. Then apply a current. If the clay has a mass negative charge it should be attracted to the positive electrode and the water should clear as the clay builds up on the electrode. If you try this nothing happens. The clay is NOT attracted to the positive electrode.

The other way to test this is to simply turn off the current. If the clay is being “attracted” by the charge as soon as the current is turned off the clay should liquify again. They did this in this experiment and the clay ball did NOT liquify. 

And again, as we have repeatedly pointed out, kitty litter is FUSED clay and doesn’t even have the tiny negative charges at a molecular level which this experiment with UNFUSED clay reveals. If this test  were run on kitty litter nothing would happen.

picture of an aquarium fish Placidochromis sp Jalo
Placidochromis sp Jalo

Testing Data

The biocenosis basket was tested in an experiment with controls and found to do NO reduction in nitrates. This year long test was done as a part of a test of Biohome and De*Nitrate filter media denitrification claims.

Four identical aquariums were set up with fish but no plants. All four aquariums had the same treatment for over one year where the nitrate levels were maintained at a high level by feeding the fish normal amounts of food. One of the aquariums had a biocenosis basket set up in it. Two of the aquariums had no way of reducing nitrates, i.e. there were two “controls”. At the end of a year and throughout the year the level of nitrates in the biocenosis basket aquarium was identical to the level of nitrates in the two controls. No reduction of nitrates was seen with the biocenosis basket.

Protomelas taeniolatius Red Empress
Protomelas taeniolatius Red Empress

The test can be found at the following link:

7.5. Denitrifying Filter Media

It has to be noted that this test was a valid scientific test in that it used “controls”.  I.e. aquariums where anoxic reduction of nitrate to nitrogen gas could not possibly occur. This is the ONLY valid way to do a test. A test with no “control” is meaningless.

Also note I did this test before I had thoroughly researched all the claims and videos on the baskets and plenums. Quite honestly I would not have gone to the trouble of doing this test if I had realized how … well … er  ….. just how strange this whole topic is. And I’m certainly not going to do any other tests. I’d feel kind of like I would be testing to see if the earth is flat or round.

OB Peacock
OB Peacock

And Dr. Novak in one of his videos complains that there are “those” who do experiments with his baskets where they only do one test (This video came out just after I posted my test of a single biocenosis basket. Hhhmmmm….. Did he mean me?). They need to do “ten tests” per Dr. Novak.

But if you look at all of Dr. Novak’s videos he doesn’t run multiple side by side tests. Indeed Dr. Novak never actually runs any true scientific experiments. As far as I can see he has never used a control. This is baffling for someone with a PhD.  A control is the bare minimum you can do conduct a scientific experiment and see if what you are claiming is correct. Similarly, if you are not using a control, you are also not performing an experiment. This is just … well … er  ….. strange!

Another test of the Biocenosis basket was done by Michael Vormwald of MJV Aquatics. He got no reduction in nitrates despite contacting Dr. Novak and getting help directly from Dr. Novak.

Labeotropheus OB Marmelade
Labeotropheus OB Marmelade

More In-Depth Analysis

Most hobbyists will be satisfied that Dr. Novak’s biocenosis basket won’t work at this point and can drop the whole thing. But there are always those of a more curious bent that want to go into more detail on this topic. For those people, read on below:

Copadichromis Borleyi Red fin Kadango
Copadichromis Borleyi Red fin Kadango

Assimilatory Denitrification

All the “research” on biocenosis or anoxic filtration becomes very understandable once one recognizes a process called “assimilatory denitrification”. The uptake by fungi, water molds and bacteria of nitrate is called “assimilatory denitrification”. It is common and well documented.

“Organisms capable of assimilatory nitrate reduction use nitrate, rather than ammonia, as a biosynthetic nitrogen source. Organisms capable of assimilatory nitrate reduction include plants, algae, bacteria and fungi. Assimilatory nitrate reduction takes place under aerobic as well as anaerobic conditions. No net removal of inorganic nitrogen is accomplished by this process, since inorganic nitrogen is converted to organic nitrogen”

“Denitrification in Recirculating Systems: Theory and Applications” van Rijn et. al 2005:
Andinocara stalsbergi Green Terror
Andinocara stalsbergi Green Terror

Dr. Franco’s “Research” on the Biocenosis Reactor

Throughout Dr. Novak’s work he constantly refers to the “research papers from Dr. Franco in Italy”. And all the other “experts” who push the biocenosis baskets do the same thing.

Finding this “research” is not easy as it wasn’t published research in a journal paper. Rather it was an “experiment” with koi ponds reported via a blog ( http://www.lagazzettadellekoi.it/ ). Dr. Franco Prati, a medical doctor who kept koi ponds in Italy, set up a koi pond with 30 baby koi, some adult koi, and 28 “biocenosic baskets”. On day 52 of the test he got this nitrate reading:

Novak Koi Pond
Novak Koi Pond

He interpreted this as nitrate level of 8 mg/l where the nitrates in the pond were identical to the level of nitrates in the water the pond was filled with. He then said that since the nitrates didn’t rise, the baskets were working.

Chuco microphthalmus
Chuco microphthalmus

This is a classic case of assimilatory denitrification. The nitrogen in the food is going to at least three things. First off the baby koi are converting it to proteins in their growing bodies. Secondly the baskets are being filled with protein rich biofloc. In addition the pond is filling with adherent algae.

The “control” here was meaningless as it was set up completely different than the experimental pond, with different stocking and turtles with some juvenile koi. The turtles output of ammonia to nitrate alone insured a “control” where the nitrate levels HAD to go up. “Controls” only have meaning if they are scrupulously identical to the experiment for all parameters save the experimental parameter.

And the Sera test was at 8 nitrate nitrogen (NO₃-N), which is 40 ppm nitrate per the API nitrate NO₃ test. The Sera test measures nitrate nitrogen (NO₃-N) and has to be multiplied by 4.4 to get the number per the API nitrate NO₃ test. AND, if the biocenosis baskets were working, the nitrates should have been zero, not 40 ppm.

So Dr. Franco did not “prove” anything. Indeed, if anything, he showed the biocenosis baskets didn’t work as they did NOT reduce the nitrates.

Fossorochromis rostratus
Fossorochromis rostratus

Other “Research”

There are several other “successful researchers” of biocenosis baskets with YouTube videos. All these sincere but mis-informed video makers have very obvious reasons they achieve reductions in nitrate other than the biocenosis basket. None of these YouTube videos used multiple aquariums which only varied in the use of biocenosis baskets, i.e. a meaningful and true experiment with controls. All have very obvious cases of experimenter bias, where the experiment couldn’t help but “support” the hypothesis.

A typical Biocenosis YouTube video is from Jay’s Aquatics (https://www.youtube.com/watch?v=5lUWQkpUvdA)  It is a heavily planted aquarium where the plants will simply absorb all the nitrates. This is very typical. Here is a photo of Jay’s aquarium:

Aquarium with a biocenosis reactor
Aquarium with a biocenosis reactor

Once again, obviously it is the plants in this aquarium which are reducing the nitrates. The reduction seen has NOTHING to do with the biocenosis basket.

A 2022 video on YouTube by Dr. Novak showcased an aquarium by “Mark” which supposedly dropped nitrates form 40 to zero. Once again note the amount of living plants in the aquarium:

Mark's Aquarium
Mark’s Aquarium

Yet another “successful” user of the biocenosis basket with a YouTube video is My Aquarium (https://www.youtube.com/watch?v=wNuurov-llw).  This enterprising soul went three weeks without a water change and had no nitrates. He said it proved the biocenosis basket he was using worked well. Here is his tank:

Aquarium with a biocenosis reactor
Aquarium with a biocenosis reactor

Note the roots of the huge emergent plant (sweet potato?). OBVIOUSLY this plant is absorbing all the nitrates.

There is another YouTube video of a “successful” biocenosis filter from Roland Wilson:

Aquarium with a biocenosis basket
Aquarium with a biocenosis reactor

Once again, note the large lush plant in the tank.

Note there is one other YouTube video where a hobbyist has a biocenosis filter in his sump with a unplanted blackwater aquarium (JPFishnut, https://www.youtube.com/watch?v=5lUWQkpUvdA). He claims to have zero nitrates after six months with only monthly water changes. The sump filter is very pristine with virtually no mulm anywhere in it, including in the biocenosis basket. But the aquarium is loaded with heavy black mulm.

Aquarium With a biocenosis reactor
Aquarium With a biocenosis reactor

But the fish loading here is very low so the amount of nitrogen going into the tank is tiny. He has a blackwater aquarium where the blackwater is created by large amounts of Indian almond leaves being added frequently and being allowed to rot in the tank. JP says the “tank has a ton of leaf litter decomposing in there“.

This “leaf litter” is a nitrogen filled mass of fungi, water molds and bacteria. The cellulose in the Indian almond leaves is providing the energy to create this biomass. Indian almond leaves have no nitrogen in them. They are 99.9% cellulose, a polymeric carbohydrate. This gives what is called a high carbon to nitrogen ratio. A high carbon to nitrogen ratio will give a lot of assimilatory denitrification, where the nitrogen gets tied up in mulm and detritus.

Copadichromis Borleyi Red fin Kadango
Copadichromis Borleyi Red fin Kadango

In this black mulm there are masses of fungi and bacteria which have taken the nitrate and converted it to proteins in their bodies. These masses of mulm and detritus are absorbing the nitrate, not decomposing nitrate to nitrogen gas. The uptake by fungi, water molds and bacteria of nitrate is called “assimilatory denitrification”. It is common and well documented.

The nitrate is NOT being reduced to nitrogen gas in the biocenosis basket. The small amount of nitrogen from the small amount of food is simply being incorporated into this leaf litter and mulm biomass. The floor of the tank is a thick black mulm.

Cynotilapia zebroides Jalo Reef
Cynotilapia zebroides Jalo Reef

The Actual Science of Denitrification

The claims of the biocenosis basket are basically the same as the claims made for Biohome and De*Nitrate “denitrifying” media. Namely that the kitty litter/laterite combination act as a filter media which reduce nitrate to nitrogen gas. So it is useful to look at denitrifying filter media as a whole.

There are designs of waste water treatment plants in Europe which do indeed reduce nitrate to nitrogen gas (“Design and Operation of Moving Bed Biofilm Reactor Plants for Very Low Effluent Nitrogen and Phosphorus Concentrations”, Rusten, 2007). These plants have established that there are several conditions which MUST be met for a biofiltration media to do anoxic decomposition of nitrate to nitrogen gas:

  • The media would have to have large amounts of organic compounds inside the media which would remove oxygen from the water by producing carbon dioxide gas (“anoxic” means “without oxygen”).
  • The media would have to have large amounts of simple organic carbohydrates inside the media which would act as what are called “electron donors” and allow the reduction of nitrate to nitrogen gas. In sewage treatment plants they add glycerin or ethanol to provide the simple organic carbohydrates.
Labeotropheus trewavasae Red Stripe Manda
Labeotropheus trewavasae Red Stripe Manda
  • The media would have to somehow move the water around inside the media particle so that each denitrifying bacterium could come in contact with the nitrate molecules it will need to function and reduce the nitrate to nitrogen gas.
  • The pores in the media would have to be large enough to allow a nitrate reducing bacteria to live inside it.
  • The media would have to be permeable enough to allow water to pass into it, be purified of nitrate and then pass back out of the media.
  • The media would have to be very impermeable to further oxygen permeation from the surrounding water.

If ANY of these six criteria are not met the anoxic decomposition won’t work. The kitty litter/laterite media in a biocenosis basket meets NONE of these six REQUIRED criteria. If any ONE of these criteria is not met the system cannot work.. This point cannot be emphasized enough.

The Biocenosis Basket Media meets NONE of these six REQUIRED criteria.

The biocenosis basket categorically cannot do any anoxic decomposition of nitrate to nitrogen gas. It simply can’t happen for no less than six separate, well established scientific reasons. 

Labidochromis chisumulae Chizumulu
Labidochromis chisumulae Chizumulu

One major problem here is that the last three criteria are mutually exclusive in a stationary media such as the kitty liter or the laterite. If the pores of a media such as kitty litter or laterite are large enough for a bacterium to live in it, then oxygen can permeate the media. If water can pass into the media, oxygen can also pass into it.  The media cannot be BOTH permeable and impermeable at the same time.

And no ceramic media has ANY organic material inside it. Ceramic media such as kitty litter or laterite has NO internal organic compounds to reduce the oxygen levels. So the inside of the media cannot possibly go anoxic or anaerobic.

There is a second reason internal organic compounds are required. These internal organic compounds are also required to provide something called an “electron donor” to the anoxic bacteria. With no organic compounds inside the laterite or kitty litter denitrification cannot take place for two well established reasons.

Cyphotilapia frontosa Six Stripe Frontosa
Cyphotilapia frontosa Six Stripe Frontosa

If one still believes in “biocenosis baskets” and “anoxic plenums”, just put these terms into a Google Scholar search. There are NO research papers on either subject. NONE. There is NO University research supporting this “technology”. If it actually worked there should be a raft of papers as it would be very useful in the billion dollar aquaculture industry. There are NONE!!! ZERO!!!

The biggest proof by far that the biocenosis basket doesn’t work comes from the thousands of “tertiary” sewage treatment plants around the world. These plants spend literally billions of dollars per year with some very complicated technology to reduce nitrate emissions by reducing nitrate to nitrogen gas. If mixing laterite with clay kitty litter worked to do this, these plants would all be using hundreds of tons of laterite and clay kitty litter in their treatments. There is not ONE treatment plant using any such technology.   Case closed.

Placidochromis electra
Placidochromis electra

Things get More Strange

Recently Dr. Novac posted a YouTube video about a “successful” anoxic kitty litter filter he had been running for several months. He had used a kitty litter that had unfused particles of clay in it (“clumping” kitty litter). The clay has become a sodden mass of, well, wet gray clay. Dr Novac went on about the fact there was no “bad smell” coming out of the sodden mass so obviously there was a healthy anoxic filter there.

This sodden mass was a putty of wet, very tiny clay particles that could not possibly pass ANY water through it. As there was no organics in it nothing was happening in the wet clay at all. This sodden mass was doing absolutely NOTHING. It categorically was not doing ANY anoxic reduction of nitrates. This is just … well … er  ….. strange!

Macrognathus acraleatus Zig Zag Eel
Macrognathus acraleatus Zig Zag Eel

Working Anoxic Devices

For more analysis of various anoxic denitrification schemes which can actually work, click on these links:

8.9.2. A Reactor Design Which will Work

For information on the science of anoxic denitrification click on the following links:

14.2.4. Anaerobic Substrates

7.5. Denitrifying Filter Media