the invention , which we refer to as a water jet moving bed biofilter ( wj - mbbr ), dramatically reduces electrical pumping and treatment costs of aquaculture type waters used in a recirculation mode of operation . the reduced energy is due to using water jets as opposed to pressurized airflow to fluidize and mobilize the media within the mixing vessel , the biological reactor or mbbr . since the water jets have no buoyancy relative to the reactor vessel , the direction of flow in the wj - mbbf can be periodically reversed to minimize problems with biofilter media bunching that results in that media becoming inactive and much less energy is used in moving the media using the water jets compared to mixing being created by air jets and flotation . use of air jets also forces a conventional mbbr to operate in only one direction , meaning the media is always following the same recurring path , i . e ., up , across , down , etc ., since the air is driving the media and the air is always moving from the bottom of a reactor vessel and upward . a mbbr filter removes carbon dioxide in the process of fluidizing the media , but there are much more efficient ways to remove carbon dioxide than by air stripping , e . g ., surface agitators . the wj - mbbr in combination with surface agitation for co 2 removal and using near 100 % efficient diffusers for adding oxygen to the overall system when needed , reduces energy use compared to conventional mbbr systems or other biological filter systems to less than 2 kwh per kg of whole fish produced , when applied to land based salmonid ( e . g ., atlantic salmon ) operation conducted at large scale , e . g ., 500 ton per year of production or larger . referring now to fig1 , a block diagram of a cross section of one embodiment of the present invention is provided . as shown , a vessel 12 contains filter media 14 . process water is received into vessel 12 from a process water inlet 16 . the process water is filtered through the filter media 14 and returned through outlet 18 . a water jet inlet 20 provides a supply of water for water jets . the water for the water jets may be process water , or any other source of water . the flow and pressure for the water jet supply water may be supplied by any suitable mechanism , including , without limitation , a pump ( not shown ). in a preferred embodiment , the water jet inlet water is divided into more than one flow path . in the particular embodiment shown , the water jet inlet water is divided into flow paths 22 and 24 , which pass through valves 26 and 28 , respectively . downstream of the valves 28 and 30 , water jets are created through openings 30 and 32 in pipes 34 and 36 , respectively . openings 30 and 32 may be sized as appropriate for the application . the openings 30 and 32 may be oriented as required for the particular application . thus , they may be formed in the sides of the pipes 34 and 36 for horizontal water jets , or at other radial locations on the pipes for water jets that emanate at other than horizontal orientations . although three openings 30 and three openings 32 are illustrated , this is an example only . more or fewer water jet openings may be used . although multiple water jet paths ( 22 and 24 , and pipes 34 and 36 ) are shown , only one path is necessary . similarly , although valves 26 and 28 are illustrated , no valves are necessary . as will be discussed in more detail below , the valves 26 and 28 allow for a preferred approach of alternating movement of the filter media . however , no such alternating movement is necessary . fig1 also illustrates header lines 38 and 40 . these header lines may be periodically coupled to the water jet pipes 34 and 36 , respectively , to create substantially constant pressure along the water jet pipes 34 and 36 , to create effective water jet pressure along the entire length of the water jet pipes . this is particularly beneficial for long runs of water jet pipes . however , no such headers are required . fig2 illustrates a portion of fig1 in detail . in the wj - mbbr , for optimal results , the geometry of the reactor vessel is critical as is the placement of the water jets that are used to fluidize / mobilize the media . the wj - mbbr takes advantage of the physical principle that rotating masses of fluid tend to break or form into circular rotating masses of fluid , which minimizes shear stress on the rotating mass ; once a mass of rotating fluid exceeds an aspect ratio of ˜ 1 . 5 , the rotating mass will break into two rotating masses so that the aspect ratio returns to nearer 1 . 0 ( a rotating cylinder of fluid would have an aspect ratio of 1 for the cross section ). for this reason , the wj - mbbr reaction vessel ( where the nitrification occurs ) is designed to have a width to depth ratio of approximately (˜) 2 , so that the mixed flow ( with properly oriented inlet jets ) will result in two counter - rotating masses of fluid , each with a long axis that parallels the long dimension of the mixing vessel . we introduce the water jets to create such a rotating flow , which consists of two parallel cylindrical rotating masses of fluid , with each rotating mass rotating counter to its parallel mate , see fig3 and 4 and arrows indicating flow direction ; note that each of these figures demonstrates one of two possible operating modes of the particular embodiment . in practice , the wj - mbbr may operate for long or short periods of time in either mode , and the modes need not be operated for equal lengths of time . the major objective and advantage of the wj - mbbr is that alternating modes and flow direction will prevent media bunching ( clumping ) if it were to occur . a conventional air - operated mbbr does not have the ability to do this in any practical way , since air is always pushing up in the same direction . the water jets can be supplied in a variety of manners and any one design approach here is not critical to the successful operation of a wj - mbbr . in a preferred embodiment , a series of slots are provided in each of the water distribution pipes . alternative methods are using a series of holes that provide round water jets . hole or slot sizes are established based upon a user &# 39 ; s criteria to minimize hole plugging by fish scales or other debris ; a typical hole or slot size would be 5 to 10 mm . a sample set of design calculations is provided below ( table 1 ). these calculations are for a 100 kg of feed per day being fed into a set of fish tanks that produce ammonia in proportion to this feed loading level . the sample calculation shows the required water jet flow is ˜ 6 % of the hydraulic loading imposed on the mbbr vessel that is necessary to maintain ammonia levels in the fish tanks at or below their design target levels . fig3 and 4 illustrate a mode of operation that includes alternating between two flow directions in order to minimize media from collecting near top of the water column ( bunching ) and becoming more resistive to water flow through the media , which therein reduces the nitrification capacity of the filter . it is important to note in fig3 and 4 that the preferred geometry of the cross section of the tank is that the ratio of the width of the tank to the depth of water being maintained is approximately 2 . an alternative embodiment would be where the reactor vessel has a diameter to depth ratio of one , but in this case , there would be one rotating mass of fluid where the center axis of the rotating body of fluid runs with the long dimension of the mixing vessel . restrictions of water depth for the reactor vessel would be a primary reason why a particular diameter depth ratio were chosen . fig4 illustrates water jet direction substantially downward from the top water jet pipe 36 , which results in the filter media rotating in the same direction as caused by the horizontal bottom jets of fig3 . this approach reduces media bunching at the top , and keeps the filter media moving . however , the water jets of pipe 36 may be oriented horizontally to reverse the flow direction of the media from that created by the bottom jets of fig3 . it should be understood that the orientation of the water jets , whether in the top or the bottom of the vessel 12 , may be varied depending on the particular needs of the system . furthermore , it should be understood that , although multiple water jets are preferred , only one water jet is necessary . also , although it is preferred that at least two rotating masses be created , the water jets may be oriented to create one rotating mass . also , the water jet or water jets need not be positioned in the top or bottom of the vessel 12 . they may be positioned anywhere in the vessel 12 . it should also be understood that the alternating operating modes discussed in connection with fig3 and 4 are examples only . various other alternating operating modes may be used , including , without limitation , schemes that employ multiple sets of water jets from multiple water jet pipes . as an example of such a scheme , multiple valves may be controlled to alternately operate multiple sets of water jets . each set of water jets results in different rotations or movement of the filter media . thus , by alternately operating the valves , the movement of the filter media may me alternated , for example , and without limitation , from two rotating masses , to reversing the direction of the two rotating masses , to a single rotating mass . as an example of another embodiment ( fig5 a , 5 b ), one or more of the water jets are located near the central axis of a vessel , which may be cylindrical . the one or more jets create a rising plume so that the water then flows upward and radially outward and then downward ( a boiling type action ) forcing the media to move up and out and then downward near the vessel walls . this motion can also be reversed with water jets oriented downward . the effect of either direction is to prevent the filter media from coalescing and becoming relative motionless . this embodiment is particularly suited for small - scale reactors , e . g ., less than 4 or 5 m 3 in total volume . preferably , for a cylindrical tank , the diameter of the cylinder is twice its depth . the particular embodiments and descriptions provided herein are illustrative examples only , and features and advantages of each example may be interchanged with , or added to the features and advantages in the other embodiments and examples herein . moreover , as examples , they are meant to be without limitation as to other possible embodiments , are not meant to limit the scope of the present invention to any particular described detail , and the scope of the invention is meant to be broader than any example . also , the present invention has several aspects , as described above , and they may stand alone , or be combined with some or all of the other aspects . and , in general , although the present invention has been described in detail , it should be understood that various changes , alterations , substitutions , additions and modifications can be made without departing from the intended scope of the invention , as defined in the following claims .