Biological Inoculation

Biofilter Inoculation Station 1m3 (BIS-1m3)

If you are interested in this equipment, contact us. 

The Bio-Inoculation Station is an automatically operated system used to inoculate the bacterial substrate used in every Aquabiotech research unit. The system can inoculate a maximum of 1m3 or 8 bio-filter medium bags (from 25 to 30 cm. in diameter and 137 cm. in height) or 32 Siporax medium filter bags (1 L) at the same time.

The bio-inoculation unit is controlled by an Inoculo-monitron controller, which maintains precise control over several parameters: the water temperature, pH, and the water make-up, as well as maintaining optimal conditions for the growth of nitrifying bacteria. Normal conditions for control are 30˚C, pH 8.2 and nitrate concentration less than 13 mg/L. The bio-inoculation unit also controls the rate of injection of growth solution and nutrients necessary for the development of the nitrifying bacteria.

The unit is furnished with an air blower used to control CO2 concentration and to provide the essential requirement of oxygen for the bacteria.

The bio-inoculation unit requires a 115V, 60Hz electrical connection and a source of de-chlorinated fresh or seawater. It is furnished with three storage tanks that contain the liquids necessary for the process of bio-inoculation: the pH buffer solution; the growth medium; and the nutrients medium. The tanks are filled manually by the operator. 



Biofilter Inoculation Station 8m3 (BIS-8m3)

The same characteristics as the BIS-1m3 but with additions allowing to easily inoculate up to 8 m3 of the bacterial substrate. Indeed, this model has the ability to automatically prepare growth and pH control solutions. Simply fill the hoppers (capacity of 22 kg) with chemicals in the form of powder, so that the system starts the process of manufacturing aqueous solutions. Subsequently, the Inoculo-monitron will inject these aqueous solutions in increasing amounts in order to automatically inoculate the bacterial substrate.

This bio-inoculation unit requires a 115V, 60Hz electrical connection and a source of de-chlorinated fresh or sea water. It is furnished with three solution tanks which contain the liquids necessary for the process of bio-inoculation: the pH buffer solution; the growth medium; and the nutrients medium.  This last tank is filled manually by the operator.  




If you are interested in this equipment, contact us. 


Technical Details

The BIS requires that the pH in the system water be maintained at a precise level. In order to carry this out, an accurate measure of pH is required. To ensure a high degree of precision, measurement of the pH is carried out in a sampler unit that is completely isolated from all interference, including any that could be caused by errant electro-magnetic waves. A solenoid valve controlled by the Inoculo-monitron situated at the circulation pump outlet opens at regular intervals to allow a sample to flow into the sampler container. A pH sensor in the container sends the measurement to the Inoculo-monitron where it is displayed. The solenoid valve then closes and the sampled water leaves the container, descending by gravity into the sump.

High-flow low-pressure air from the blower is injected at the base of the incubator tank. The blower sends the air flowing up the tank counter-current to the water flow.

The incubator tank lid is provided with a chimney, which exhausts the air that was injected by the blower. The chimney is designed so that humidity trapped in it can drain out by means of a vinyl tube connected to the unit drain.

The design of the incubator tank makes it efficient at both CO2 degassing and oxygenation. The high air-to-water ratio and large contact area within the incubator tank maintain the CO2 level below 15 mg/L and the water well oxygenated.

The Filtration Module has been designed to keep the biofilm thin and active for optimal nitrification.  A thin biofilm favours diffusion of CO2, ammonia, and oxygen.  The high flow rate across the bioreactor allows it to be self-cleaning because of the constant shearing of excess microbial biomass.  Starting and stopping the flow in a biofilter increases local agitation and favours the sloughing off of excess biofilm that may have accumulated on some parts of the biofilter.  Sloughing off is normal and useful.

 Advantage Suitability to Application


No backwash is required;
No daily maintenance required – operator peace of mind;
Simple and economical to operate;
Stable water quality – avoids backwashes that disrupt bacterial activity;

Absence of flow limitation within the bio-reactor – the biofilter can take nearly unlimited flow rate ;

Important in regard to system management: flow rates can be increased to supply growing oxygen demand as fish density increases without limitations imposed by the biofilter;

A high flow rate across the biofilter favours nitrification, as it keeps the biofilm thin and active, and provides superior oxygen and ammonia diffusion across the biofilm;

Low operating pressure

Reduces pumping costs.  The water needs simply to be pumped to the top of the biofilter.  It then trickles down through the media without pressure build-up.

No gradual reduction of water flow across the biofilter

Very important for operator peace of mind.  As there is no gradual clogging, the flow rate across the biofilter remains constant, nor is there any variation in water exchange rates within the fish tanks.

Very light media with electrostatic affinity for bacterial cells; supports high pressures

Reduces transportation costs.  Easy to manipulate.  Rapidly and efficiently coated with nitrifying bacteria.  Resists compacting.

Biofilter provides excellent oxygenation and degassing


Enhanced security of biofiltration process through:

o   The addition of oxygen as water trickles down

o   The absence of anaerobic zones, noxious odours, within the biofilter

o   Prevention of CO2 accumulation within the system

o   Increased operational economy through

o   The contact with air provides oxygen for nitrification

o   The addition of a degassing column is not required

Negligible water loss

Ideal for closed systems

The energy output from the oxidation of ammonia and nitrites is considerably less than that from organic compounds. As a result, the microorganisms have a very slow growth rate. Reproduction time in pure culture is 8-24 hours. In effluent water, it is 20 to 40 hours. Their numbers are rapidly exceeded by those of heterotrophic bacteria in the presence of organic matter. Some of the heterotrophic bacteria are known to double their numbers in as little time as half an hour. It is for this reason that we make sure that a sufficient population has been implanted in the Aquabiotech system biofilters before delivery.  The proprietary method used for biofilter activation ensures a dynamic and efficient biofilter operation, even when it is connected to well-loaded fish tanks.  Periodic additions of sustaining bacteria are not required.

After start-up, biologic filters can operate for several years without backwash. Depending, of course, on the use to which they are put, they may even improve with age as other microorganisms become implanted.  We recommend the following elementary precautions in order to guarantee optimal performance.

  • Do not disturb or wash the bacterial support.
  • Maintain water pH above 7.0 at all times and alkalinity above 100 mg/L.
  • Prevent the entry of organic matter in the biofilter in order to limit the growth of heterotrophs.
  • The rate of exchange water (water make-up) must be less than the speed of reproduction of nitrifying in water (12 to 24 h).

As nitrifying bacteria do not survive a long time without organic pollution, it is important to provide inorganic nutrients when you remove all fishes.  In this way, the biofilter remains active between two experiments.

Temporarily stopping the flow of water will not affect the bacterial biofilm, as the sump is full of water. Indeed, the humidity will keep the active biofilm for one to two weeks. A longer period requires re-inoculation of the biofilter when you restart the unit recirculation. Following an interruption of several months, allow at least 6 weeks for re-inoculating the biofilter.

The practice of good management is particularly important in the operation of a closed system.  A biofilter is similar to a living organism; an increase in feed rate may give rise to a temporary increase in TAN and nitrite, and it may take a few days for the bacteria to adapt to this new regime. It is, therefore, most important to keep a tight control on the rate of feed to the aquatic organisms. If supplementary biomass is introduced, it must be followed by increasing the feed rate gradually.  The colder the water, the longer it will take for the biofilter to adapt to an increase in feed rate.

The optimal temperature for nitrifiers in a temperate climate is known to lie generally between 25 and 30°C.  An immediate consequence of using cold-water recirculating systems is the reduced growth rate of nitrifiers and their lower oxidation rate. Regardless of temperature, the growth rate of nitrifiers living in a relatively “clean” environment remains significantly higher than nitrifiers in activated sludge. Point of interest to note: the available data also indicate that the bacterial biomass is less sensitive to variations in temperature than the cells in suspension.

On the other hand, it is known that half saturation constants (Ks) of nitrifiers decrease considerably with decreasing temperature.  For example, the half-saturation constant (Ks) of Nitrobacter sp. goes from 2.67 at 25ºC to 0.30 at 10ºC.  It is thus clear that low levels of ammonia and nitrite can be achieved more readily in cold water than in warm water systems.

Management practices are influenced by this phenomenon of reduced activity of nitrifiers in cold water.  Our biofilter has been sized for a maximum 0.8-kg dry food per day at 15ºC or more.  If the water is colder, it can be assumed that the feeding rate will be less than 0.5 kg to account for the reduced appetite of fish.  If fish appetite is not reduced by cold water, you should watch the biofilter closely, for it is reasonable to assume that the nitrifying capacity of the biofilter will have decreased.

Frequent water flows stop and start in the biofilter causing biofilm sloughing. It is therefore important to minimize this fact. Under conditions of a continuous and heavy charge of biologic material, this kind of sloughing off can naturally occur every two or three months. It may result in a temporary increase in the turbidity of the water for a day or two.  It is recommended to increase the proportion of water make-up to minimize the discomfort for aquatic organisms. A preventive treatment with chloramine is also suggested. To minimise this temporary turbidity, it is suggested to trigger this sloughing off by interrupting the flow through the biofilter for few seconds once a month.  This action will prevent biofilm build up.

A biofilter may be stored for several months without problem. The nitrifying bacteria are able to survive for a considerable time with very little attention. We recommend to simply keep the lid shut in order to conserve the humidity of the media. The bacteria must be protected from direct sunlight and freezing. Before storing the biofilter, make sure the purge has been emptied and that only a thin layer of biofilm covers the media. In general practice the support would already be very clean and coated with a thin, grey, gelatinous deposit.


Desired Range


Suspended Mater, Turbidity

Less than 2 mg/L of suspended matter and less than 5NTU are recommended

Turbidity and suspended matter are the primary carriers of Biological Oxygen Demand (BOD), whitch favour the growth of heterotrophic bacteria to the detriment of nitrifiers.  May hinder the performance of bioreactors.


More than 100 mg/L

Alkalinity maintains the pH level and favours the passage of inorganic carbon through the bacterial cell wall.


Between 7.3 and 8.8

High pH favours ammonia oxidation; low pH values (below 7.0) inhibit Nitrosomonas sp.

Dissolved oxygen

More than 6 mg/L

Nitrifiers require oxygen to survive.  The nitrifying bacteria consume 100 to 300g of oxygen per kg of food distributed to fish.  A high oxygen level will favour the passage of O2 across the microbial film.


Between 7 and 30 C

Even though nitrifiers grow faster at high temperatures (25-30 C), once they are established they will remain active at low temperatures.


Minimize water sterilization

UV or ozone destroys nitrifying bacteria in suspension. Consequently, the bacteria released into the water through the biofilter can grow and colonize the recirculated water. Moreover, their ability to bind to solid surfaces is reduced.

Users of this Technology

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