BIOLOGICAL FILTRATION IN AQUARIUMS AND PONDS

Biological Filtration is the process whereby potentially toxic organic substances are removed by filtration from aquariums and ponds by being consumed by various beneficial nitrifying bacteria that utilize them as a natural food source.  These bacteria are attracted to and become attached to the water filter materials.  This process is also called in aquarium and pond keeping the "Nitrogen Cycle," but for aquatics this is only a small part of this complex environmental cycle in nature.  The bacteria involved in what aquarium and pond-keeping know as the "Nitrogen Cycle" are the same as those involved in Biological Filtration.  And the process is the same.

These nitrifying bacteria in biological filtration and the aquatic nitrogen cycle are in the beneficial gram positive group of bacteria, and their presence is important to aquarium and pond keeping.  These bacteria are harmless to the aquarium inhabitants, as well as to man, pets, and other life, and do not cause any disease problems.  They like to stick to positively charged surfaces, such as glass, gravel, and other substrates, filter materials such as filter pads, activated carbon, ceramic Raschig rings (see Kordon Bio-Mech) and glass decorations.   They do not thrive on plastic, such as used in filter balls, or on the walls of plastic aquariums, or on plastic decorations.  In fact, for those aquarists wanting for some reason to keep these bacteria low in number, they only need to be sure that as much as possible everything in their aquarium is plastic. 

Small numbers of these bacteria will come into the aquarium and pond on the surface of the fish, invertebrates, or aquatic plants, or through moist air, or in natural food. Also, these bacteria can be provided by commercial culture products (see Kordon Zym-Bac) or by introducing some gravel or filter material from a well established aquarium or pond which already has gone through the nitrogen sequence. A cubic inch of gravel or filter material per ten gallons of water is sufficient. Given an adequate food supply, oxygen and a suitable substrate, these bacteria will quickly spread throughout the new gravel and filter bed.

Nitrifying bacteria typically establish themselves on the surface of the gravel, the inner surfaces of the aquarium or pond, inside filter tubing, and anywhere else that has a water flow resulting in good oxygen levels.  Keep in mind that the greater the number of gram-positive bacteria, the greater take up of oxygen from the water.  Ample aeration is needed so that the fish and aquatic invertebrates do not suffocate.

Uneaten food, dead and decaying animals and plants, as well as the fecal, urinary and respiratory waste products of the animals are broken down  into ammonia by nitrifying heterotrophic bacteria in a process called ammonification. Also, a large part of the excretion of fishes is already in the form of ammonia. Within the restricted volume of an aquarium or pond, and in the absence of an established colony of nitrifying bacteria, ammonia can increase quickly to toxic- even lethal- levels. Ammonia can place a high level of stress on fishes, especially those that have been recently moved or handled. In sufficient quantity in the water Ammonia is lethal.  All efforts should be made to reduce these stress and toxic levels.  So having colonies of nitrifying bacteria in aquariums and ponds is important.

How to Detoxify Biological Filtration and the Aquatic Nitrogen Cycle in Aquariums or Ponds
For new tropical aquariums (water temperatures of 72 degrees Fahrenheit, 22 degrees Centigrade) use a regular dose of Kordon AmQuel Plus water conditioner at the time the water is added.  Repeat dosage twice a week for five weeks.  After that add a single dose once a week, or when making water changes, in order to detoxify any of the nitrogen compounds in the water.

For new unheated aquariums or new ponds use a regular dose of Kordon Amquel Plus water conditioner at the time the water is added.  Repeat dosage twice a week until the nitrogen cycle is completed.  In water above 72 degrees F (22 degrees C) continue to treat as indicated above for new tropical aquariums.  For colder water above 60 degrees F (16 degrees C) repeat dosages twice a week for 10 weeks.  After that add a single dose once a week, or when making water changes, in order to detoxify any of the nitrogen compounds in the water.  Below 60 degrees F (16 degrees C) repeat dosages twice a week for 20 weeks.  After that add a single dose once a week, or when making water changes, in order to detoxify any of the nitrogen compounds in the water.

For instructions in how to accelerate the nitrogen cycle by use of autotrophic bacteria, see below, and in the last sections in this Article.  

The Use of Water Quality Test Kits
The use of a high quality test kit (such as Kordon's Ammonia Water Quality Test Kit) is  important at this stage of an aquarium's or pond's existence for those wanting to monitor their aquarium conditions (see the Kordon Articles "Insights Into Water Quality Test Kits" and "What Every Aquarist and Pond Keeper Should Know About Ammonia Test Kits").  Ammonia in the water from 0.25 ppm = mgL or above can be toxic to fishes.  All levels and forms of Ammonia in the water can be easily detoxified with the use of AmQuel®, Kordon's ammonia removing water conditioner.  or by the use of AmQuel Plus.  Also, all of the toxic organic nitrogen compounds (including ammonia/ammonium, nitrites, nitrates, pheromones) are detoxified/removed by using the more advanced Kordon Amquel Plus® product.

More about the Nitrogen Cycle
Following the ammonification part of the cycle, two groups of autotrophic nitrifying bacteria become established in sequence. The nitrifying bacteria, in a process called nitrification, use the ammonia as food, thereby eliminating it from the water. The first group of nitrifiers oxidize ammonia NH3 into nitrite NO2. In a new tropical aquarium set up in which the bacteria of the nitrogen cycle are not in balance, the high ammonia level declines within an average of 1-2 weeks or more. Ammonia is replaced by a rising level of nitrites, typically within an average of 2-3 weeks or more. The sequence is slower, the lower the water temperature in the aquarium or pond. 

Nitrite is stressful and toxic to freshwater fish and is stressful but somewhat less toxic to marine fishes and aquatic invertebrates.  Its concentration in the aquarium or pond needs to be carefully monitored with a good quality test kit such as Kordon's AquaTru® Nitrite Test Kit. Nitrite level should be kept as near zero as possible.  The simplest way to control Nitrite in the water is to dose with Kordon Amquel Plus.  Also see the Kordon Article "Insights Into Water Quality Test Kits".

If AmQuel Plus is not used, as the nitrite levels rise above .2 ppm (mgL), careful attention should be paid to the action of the fish. If any unusual behavior or stress is observed, immediate action should be taken to improve the situation. For fresh water fishes, the addition of some salt to the water coupled with a partial water change, may help solve the problem.  When conditions are stable, eliminate the salt level in the water, because leaving the salt long term in fresh water can be stressful to many kinds of fishes.  For marine fishes, a partial water change should be performed. Note the level of Nitrite indicated on the test kit at the time of the problem and continue monitoring the Nitrite levels, making water changes as indicated by the readings.

The final stage in aquarium and ornamental pond situations is Nitrate NO3. In the past Nitrate was considered nontoxic even at levels as high as 60 to 80 ppm (mgL) in freshwater and 10 to 20 ppm (mgL) in salt water. However, recent scientific studies show that the physiology of freshwater and saltwater fishes and some aquatic invertebrates are adversely affected by Nitrate levels above 10 ppm (mgL).   For some invertebrates including some corals, anemones etc., Nitrate levels can be more critical, and its level needs to be below 10 ppm (mgL).  This may be true for some aquarium fishes as well that have yet to be scientifically studied. 

Toxic levels for your particular aquarium or pond situation can best be determined by careful monitoring of the Nitrate levels and close observation of the aquarium or pond residents. Levels as high or higher than these should be corrected by the use of Kordon's AmQuel Plus or by water changes.  Also, Nitrates can be removed naturally by a process called denitrification, but this is risky and best left to those with a high degree of skill and experience. For the rest of us, Nitrate is most easily removed by using AmQuel Plus or performing regularly partial water changes.

With all this said, there are simple ways to handle biological filtration and the nitrogen cycle to keep it nontoxic to aquatic life

First is not to leave it to chance as to whether you are getting the right bacteria in aquarium and pond keeping.  No matter what the water conditions, it is important to have the right bacteria dominant for nitrification.  The best way to do this is to introduce the right bacteria from the start.  This can be done with long-term domesticated nitrifying bacteria specially cultured, for which Kordon's Zym-Bac is strongly recommended.  it comes in two forms -- fresh water and salt water.  See Kordon Article "The Importance of Using ZymBac tm When Starting a New Aquarium or Pond" for a useful further explanation of the role of nitrifying bacteria, and about these Zym-Bac products. 

Second, as an added protection, is to use regularly Kordon AmQuel Plus.  It is simple and easy to use, and it permanently detoxifies within five minutes of treatment, all of the toxic organic nitrogen compounds in the water, according to amount of dosage.  A single dose eliminates all toxicity in all kinds of water conditions, at least to 1.2 ppm Ammonia/ammonium, 2 ppm of Nitrites, and 13 ppm of Nitrates.  this reduces the need to make water changes, and the need to continually have to use water test kits to check water conditions.  The AmQuel Plus takes care of detoxifying all nitrogen compounds, doing this without fail for you. 

More About Using Water Quality Test Kits to Monitor the Progress of Biological Filtration.
For further information on water test kits see the Kordon Article "Insights Into Water Quality Test Kits."

In general the most important water test to be done regularly is for pH (alkalinity/alkalinity) of the water, because it is a good indication of water quality.  Use a pH kit regularly to be sure that the acidity is not increasing (and the alkalinity is not decreasing). A drop in pH indicates that water conditions are worsening. Below a pH of 6.5 in fresh water, and 8.0 in salt water, the bacteria associated with the nitrogen cycle will progressively cease to function, disrupting the cycle. When the cycle is disrupted, ammonia levels (the toxic form of ammonia/ammonium) will rapidly increase.  For additional details on pH, click here: pH TEST KITS

For those wanting to be informed about the levels of nitrogen compounds in the water, at ;east use an ammonia test kit the first weeks after an aquarium or pond is set up to monitor the nitrifying bacteria's progress in removing the potential build up of toxic Ammonia. Monitoring the cycle will insure that, after the first week in tropical conditions (longer in colder water conditions), the Ammonia is not reaching toxic levels, and after its peak, it  is steadily declining and then disappearing. Check for ammonia at later intervals to be sure the cycle has not been disrupted. For additional details on Ammonia, click here: AMMONIA INFO

In the second and later weeks use a Nitrite test kit to be sure nitrite is not reaching toxic levels, is progressively declining and then disappears. A nitrite reading is an indication that the bacteria are becoming established and functioning. Use a nitrate test kit to monitor the rise in organics over the ensuing weeks and months. To lower nitrate levels in the water do periodic water changes or use Kordon AmQuel Plus. 

Some Commonly Asked Questions Concerning Biological Filtration and the Nitrogen Cycle:

Why haven't I heard or seen more about the use of Kordon's AmQuel Plus in regard to biological filtration and the nitrogen cycle?  This product is relatively new and just becoming known.  Also, it is such a major breakthrough in making aquarium and pond keeping easier, particularly for newly set up aquaria that for all these past decades have been prone to suffer from "New Tank Syndrome," that it is hard to believe that AmQuel Plus is true to its claims.  Believe us, it was tested for years,  including by numerous independent scientific laboratories, and it indeed performs as claimed. 

What about the use of Kordon's AmQuel or AmQuel Plus in removing toxic nitrogen compounds?  Will this in any way interfere with biological filtration and the "nitrogen cycle"? In both fresh and salt water, AmQuel and AmQuel Plus combine with the Ammonia molecules, forming new molecules that are irreversibly nontoxic. The nitrifying bacteria utilize these new molecules as a food source just as they do with the original ammonia molecules.  The AmQuel products do not in any way interfere with biological filtration or the nitrogen cycle.  AmQuel Plus or AmQuel are the easiest way to totally eliminate toxic ammonia in the water without disrupting the nitrogen cycle. Amquel Plus is the easiest way to take care of all of the individual stages of the nitrogen cycle through Ammonia/ammonium, Nitrites, and Nitrates.  Regular Amquel only detoxifies the ammonia, and not the other nitrogen compounds.  For additional information on either of these water conditioners, click here for Kordon AmQuel Plus, or here for Kordon AmQuel. 

As for all the nitrogen compounds involved with biological filtration and the nitrogen cycle -- Ammonia/ammonium, Nitrites and Nitrates -- these are irreversibly detoxified by Kordon AmQuel Plus.  As stated above for Ammonia, AmQuel Plus is the easiest way to totally eliminate all the toxic Ammonia, Nitrites and Nitrates in the water without disrupting the nitrogen cycle.

What about products that claim to speed up or eliminate the nitrogen cycle?   So far as we know, there are no products that eliminate the nitrogen cycle, and when it is totally detoxified by the use Kordon's AmQuel Plus, it is still going on, but is safe for aquatic life, including fishes.  The way to speed up the nitrogen cycle is to use products with the proper autotrophic bacteria.  Kordon's Zym-Bac products are recommended for doing this.  See Kordon Zym-Bac for further information.

What else should I know about the differences in the bacteria and biological filtration between fresh and saltwater conditions?  The bacteria are entirely different between fresh and salt water (see Kordon Article "The Importance of Using Zym-Bac tm When Starting a New Aquarium or Pond" . Therefore, while the sequence of events in the nitrogen cycle are the same, the exact timing will vary and the ranges are narrower in salt water. Also salt water provides lower oxygen levels than does fresh water. The bacteria associated with the nitrogen cycle need oxygen and will progressively cease to function at lower oxygen levels. Natural sea water pH is 8.3 and lowering pH levels severely adversely affect the metabolism of the saltwater nitrogen cycle bacteria. Saltwater conditions need to be monitored more accurately than for comparative freshwater conditions.