Anoxic Filtration System: Testing 11 commercial products claiming to contain nitrifying bacteria that will facilitate in the conversion of toxic ammonia to nontoxic nitrate within the pond.

Cat litter from Meijer’s Food Stores…You can buy this once or you can every year buy nitrifiers cultures and hope they will work. In fact, contact the manufacture of anyone of the nitrifying bacteria products for sale and see if they will tell you exactly what is in their product or if they have any scientific lab test to show it works as clamed. I’m not talking anecdotal accounts; I’m talking about independent lab test of their products validity. Good luck!

We just had a pond install in our backyard about three years ago and the contractor told us that after cleaning out the pond in spring we were to add a commercial product that would help reestablish the bacteria in our pond. My question is: Can you help us determine what is in these bottles and freeze-dried containers of bacteria that we have to add to our pond? When we asked the professionals and/or experts they say, “I do not know,” are they are not very specific on exactly what kind of bacteria they are using, so please help us. Because some the products we use seem to work and other products, do not!

When information, which properly belongs to the public, is systematically withheld by those in power, the people soon become ignorant of their own affairs, distrustful of those who manage them, and—eventually— incapable of determining their own destinies.

—Richard M. Nixon

This time it appears you came to the right person to ask your question to. Despite the numerous books written by several competent authors about the role of nitrifying bacteria in the pond, most of the information in general remains anecdotal. This is particularly true when it comes to nitrifying bacterial products sold to add bacteria to the pond and enhance nitrification or to inoculate replacement bacteria in the ponds filter.

First, let us get down to the facts of what is known. True nitrifying bacteria are those belonging to the bacteria family Nitrobacteriaceae. The strictly oxygen requiring aerobic bacteria requires carbon dioxide as their source of carbon and they can use inorganic compounds such as ammonia and nitrite as their source of energy. Because of their abilities to detoxify inorganic materials the classification nitrifying bacteria are autotrophs, accurately meaning “self-feeders.” You can find nitrifying bacteria in the soil, freshwater systems, and the oceans settlement deposits. Known are five ammonium oxidation bacteria; two of these genera contain marine strains. Also known are three nitrite-oxidizing genera, all of which contain marine strains. The beneficial role of nitrifying bacteria within a pond environment is their function in the nitrogen cycle. Nitrifiers perform the biological oxidation of ammonia to nitrite in a two-step process wherein ammonia will be oxidized into nitrites, which subsequently then is oxidized to nitrates.

During this process of nitrification, Nitrosomonas spp., Nitrosospira spp., and Nitrospira spp. converts toxic ammonia /ammonium to nitrites; this is also toxic to the pond inhabitants. Nitrites can be highly toxic to freshwater fish but is less so when dissolved salt is added to the pond, for it will then act as a detoxifier in these waters. In the second step, nitrites are converted to nitrates by Nitrobacter spp. and nitrates or not generally considered toxic unless accumulated in high concentrations. However, we must also make note that in natural systems cyprinid exposed to nitrate levels above 2-3 ppm are seldom if ever encountered. We also have known that high levels of the nitrates are a contributing factor to suppressing Koi colors and their ability for releasing toxins along with contributing as a food source to cyanobacteria (Family: Cyanophyta) along with very minute levels of phosphates.

There are numerous commercial products claiming to contain nitrifying bacteria that will facilitate in the conversion of toxic ammonia to nontoxic nitrate within the pond. However, on the labels [Ed: That’s if they have a label that lists anything at all.] of some of these products addition to nitrifiers, some products contained other bacteria such as Bacillus, Streptococcus, Pseudomonas, Staphylococcus, and Escherichia coli (E. coli). Now we come to the main problem about these particular bacteria, they are not nitrifying bacteria and therefore cannot successfully convert ammonia to nitrates. Bacteria such as these are classified as heterotrophs; that is, they cannot utilize carbon dioxide but required one or more complex organic compounds as a source of carbon. Heterotrophic bacteria compete with nitrifiers for available space, oxygen and in some situations ammonia. When the organic load is high, heterotrophic numbers increase which can lead to a depression in nitrate formation in biological filters.

Some evidence indicates that rapidly growing heterotrophs produce intermediate byproducts, which are toxic to nitrifiers. Several heterotrophs, particularly the coli form of bacteria, can readily convert nitrates back to nitrite in a reduction process. Therefore, this ability is a characteristic of the bacteria family Enterobacteriaceae, which includes the E. coli and other related coli forms of bacteria and pathogens such as salmonellae. Reducing nitrates to nitrites commonly used as a diagnostic test more often in clinical microbiology labs. Then other bacteria such as Pseudomonas spp. or Bacillus spp. can further convert nitrites to ammonia.

In our ponds nevertheless, nitrification in reverse (nitrates reduced to nitrites and then again reduced to ammonia in anaerobic conditions.) can cause severe problems in water quality. This reverse situation usually occurs when oxygen concentrations are lower than .050-ppm, pH begins to drop, or an overload of organic material is present. Which are the right conditions for a filter that is congested with organic matter. In these situations, that heterotrophic bacteria population can “bloom” (aka: “Bacteria bloom,” turning the turbidity of the water white) and further contribute to water quality problems. Nitrifying bacteria have long generation times and maybe eclipsed by a “bacteria bloom” of heterotrophs. Correctly implemented UV sterilizers will help in these situations.

Laboratory experiments were conducted to determine the efficiency of commercial products available to the pond hobbyists. The laboratory experiments tested and analyzed over 11 different products for freshwater systems. Out of these 11 products, seven of them claim efficiency in both fresh and saltwater so testing under both conditions was conducted. These studies conducted were not under pond conditions, but rather under laboratory conditions to stimulate optimum growth, were there would be no competition from heterotrophs. A meticulously maintained, optimum oxygen level throughout the testing was held at a constant, the pH was carefully controlled, and a diet of ammonia and carbon in a chemical medium (ATCC 221) was provided. All freshwater products were grown on this medium, while saltwater products grown on specially formulated medium (ATCC 928). In the tests, all the nitrifiers had to do was eat, grow, convert ammonia to nitrate, and reproduce. All the cultures ran in duplicate and shaker baths and maintained at 27° C. (77° F.). Sterile calcium carbonate chips added to the medium to provide attachment surfaces for the nitrifying bacteria. All the experimental products used, according to manufacturer directions. The experiments conducted were for two weeks, which all parameters of ammonia, nitrite, nitrate, and pH measurements were every two days to determine the progress of nitrification.

Parameters were determined by using a spectrophotometric analysis using the Hach, DR/2000. All ammonia measurements conducted, using the Nessler method, nitrite using the ferrous sulfate method, and nitrates using the cadmium reduction method, respectively. Out of the 11 products tested only one product excelled in converting ammonia to nitrite to nitrate. This particular product produced ammonia depletion in 4 to 5 days earlier than all the other products. The remaining freshwater commercial sources moves at various rates through the process of converting ammonia to nitrate. Some of these products fail to show any movement at all while others cause a reversal of the nitrification process, causing the conversion of nitrate back to ammonia.

The research conducted with the nitrification bacteria concluded that ammonia is being produced constantly in an enclosed environment such as our ponds. Small amounts of ammonia are being produced from diffusion across the gill membranes of the fish, but a majority of ammonia is produced through the process of mineralization, which involves the conversion of waste products in the pond to ammonia by heterotrophic bacteria. Therefore, products that are capable of converting toxic ammonia to nontoxic or less toxic nitrates can be an essential part of any pond environment.

In the 11 products tested and compared in the laboratory, the findings were that only two products perform faster and at superior levels to all other products. These high levels are due to use of pure cultures of live Nitrosomonas, Nitrosospira, Nitrospira, and Nitrobacter bacteria. The other products using a combination of Nitrosomonas, Nitrosospira, Nitrospira, and Nitrobacter bacteria at lower levels in conjunction with Heterotrophic bacteria; while some of the other products tested contained Heterotrophic bacteria alone. Using Heterotrophic bacteria as a supplement or a replacement for true nitrifying bacteria belonging to the family Nitrobacteriaceae is not an uncommon practice, because Heterotrophic bacteria are able to tolerate a wider range of environmental conditions. Heterotrophic bacteria used in place of true nitrifiers lead to a number of basic problems. In two of the experiments that were performed, heterotrophs under certain environmental conditions such as low pH and oxygen levels can operate in reverse directions, converting nitrates back to nitrite, ammonia, and nitrogen gas, which are called denitrification.

It should also be known that the Heterotrophic bacteria used in these products are also capable of forming spores, allowing the product to be dried or freeze dried, packaged, and sold as a viable culture. Products containing Nitrosomonas, Nitrosospira, Nitrospira, or Nitrobacter spp. cannot readily undergo this drying process; however, in liquid formulations the nitrifiers can survive as valuable inactive cells, which can be reactivated during periods of mineralization.

Found from these laboratory studies, that dry products perform at some of the lowest levels in the conversion of ammonia to nitrate when placed in an optimal in vitro environment. Other experiments have shown that there is often the problem of competition for ammonium between the Heterotrophic bacteria and the true nitrifiers, nitrifying bacteria being less competitive than the heterotrophs. These findings were further supported by the results, which show that pure nitrifiers’ cultures far outperform those products containing a mixed culture of nitrifiers and heterotrophs. It was concluded that in the lab under the most maintained optimum growth conditions during its study and if a product did not perform under these conditions it is less likely to perform under pond conditions.

In conclusion, there are products available on the market that work exceptionally well; it is up to the hobbyists /consumer to find through experimentation and trial and error, which products work for them. However, you must also remember, that these products are not a replacement for good husbandry and proper pond maintenance. No product, no matter how well it works can replace a properly designed filtration system.