Apparatus and system for aquaculture

Abstract

The present invention generally relates to systems and devices for aquatic crustacean and fish species rearing.

Description

Technical Field

[0001] The present invention generally relates to systems and apparatus for the cultivation of aquatic crustacean and fish species. Background Art

[0002] The increasing demand for lobsters, fish and related aquatic species is driving the need for improved aquaculture technologies to provide a reliable source of seed. In addition to the need for these technologies, there is a growing demand for sustainability among fisheries and those involved in aquaculture. This not only protects the breeding stock and maintains the environment in which it lives, but also improves the economic returns of the fishery and the industry as a whole.

[0003] Aquaculture of shellfish and other marine species is based on broadly similar principles, although the specific equipment used and the processes followed may vary from species to species and depend on other requirements.

[0004] For example, the development of aquatic crustaceans involves different stages, including transitions through successive molting cycles and subsequent morphological changes. For example, the successful production of lobsters through the larval stage depends on the success of each molting cycle. This in turn is closely related to the rearing conditions of the lobster broodstock.

[0005] The design and features of hatcheries that ensure the successful culture of lobsters and other aquatic species include the shape and design of the containers in which they are cultured, as well as the water quality and cleanliness. Plankton Kriesel-type tanks are commonly used to raise lobster larvae, and small-scale Kriesel-type tanks are often used. As experimental containers, these systems are often extremely useful. The disadvantages of Kriesel-type tank designs previously used for commercial applications include the inability to increase the size of the system while maintaining favorable fluid dynamics. Factors such as the buoyancy of the larvae and their feed and interactions within the culture container are very important. In addition, the shear force generated by the water flow needs to be minimal to reduce physical damage and mortality to the larvae.

[0006] The present invention seeks to address some of the disadvantages of prior art devices and systems in the field of aquaculture. Summary of the invention

[0007] The present invention is based (in part) on the discovery that the survival of larval lobsters can be improved by engineering containers (and systems containing such containers) with specific parameters including culture water hydrodynamics and water quality. The present invention results in increased larval viability and successful growth and development of the animals beyond the initial larval molt.

[0008] According to a first aspect of the present invention, there is provided a recirculating aquaculture system (RAS), the system comprising:

[0009] (i) Drum filters;

[0010] (ii) biological sewage filtration tanks, or bubble bead filters;

[0011] (iii) at least one ultraviolet sterilizer;

[0012] (iv) a foam separator with an ozone injection device or a separate ozone injection device;

[0013] (v) at least one ozone contact tank or conditioning tank of a volume equal to or greater than the volume of the larval rearing tank;

[0014] (vi) optionally at least one degasser;

[0015] (vii) activated carbon filter;

[0016] (viii) bag filters;

[0017] (ix) optionally at least one secondary UV ozone decomposer;

[0018] (x) at least one larval rearing (or culture) tank having a volume of greater than or equal to about 10,000 liters.

[0019] In an embodiment, the aforementioned RAS is characterized in that features (i) to (x) are in fluid contact with a flow of seawater passing through the system in the order from (i) to (x).

[0020] In an embodiment, the aforementioned RAS is characterized in that fresh seawater is introduced into the system at the deaerator.

[0021] In an embodiment, the foregoing RAS is characterized in that new seawater is introduced into the system from at least one ozone contact tank or water conditioning tank having a volume greater than or equal to about 10,000 liters.

[0022] According to another aspect of the present invention, there is provided a method for pre-treating seawater for aquatic larvae breeding, comprising the following steps:

[0023] (i) Foam separation;

[0024] (ii) ozonation;

[0025] (iii) activated carbon filtration;

[0026] (iv) ultraviolet disinfection; and

[0027] (v) Ultraviolet ozone destruction.

[0028] According to another aspect of the present invention, there is provided a larval rearing (or cultivation) tank having a volume of about 10,000 liters or more, wherein the cultivation tank is a substantially circular tank, characterized in that it has a substantially centrally located water inlet pipe (1), the water inlet pipe extending above the water level of the tank and terminating substantially near the bottom of the tank, and having an outer surface exposed to the water of the tank and an inner tube cavity (2), wherein the upper surface of the outer surface of the water inlet pipe is mounted with a conical mesh sleeve (3), the conical mesh sleeve being fixed to the water inlet pipe below the surface and extending outwardly above the water level of the tank, and wherein the lower surface of the outer surface of the water inlet pipe is also mounted with a conical sleeve (4), the conical sleeve may be mesh or solid, the conical sleeve being fixed to the water inlet pipe below the surface and extending outwardly toward the base of the tank below the water level of the tank, wherein the inner tube cavity maintains a constant supply of seawater toward the base of the tank.

[0029] In an embodiment, the water inlet pipe (1) is characterized in that it has an inner lumen (2) and an outer lumen (5), the outer lumen accommodating at least one water inlet supply line (6) to allow additional seawater to enter the tank from above the surface of the tank.

[0030] According to another aspect, the present invention provides a water circulation assembly for an aquaculture tank, the assembly comprising an inlet pipe (1), the inlet pipe extending above the water level of the aquaculture tank and terminating substantially near the bottom of the aquaculture tank, and having an outer surface exposed to the water of the aquaculture tank and having an inner tube cavity (2), wherein the upper surface of the outer surface of the inlet pipe is mounted with a conical mesh sleeve (3), the conical mesh sleeve is fixed to the inlet pipe below the surface and extends outwardly above the water level of the aquaculture tank, wherein the lower surface of the outer surface of the inlet pipe is also mounted with a conical mesh or solid sleeve (4), the sleeve may be mesh or solid, the conical sleeve is fixed to the inlet pipe below the surface and extends outwardly toward the base of the aquaculture tank below the water level of the aquaculture tank.

[0031] In an embodiment and with reference to the water circulation assembly, the water inlet pipe (1) is characterized by having an inner lumen (2) and an outer lumen (5), the outer lumen accommodating at least one water inlet supply line (6) to allow additional seawater to enter the aquaculture tank from above the surface of the aquaculture tank.

[0032] The water movement in the culture box is characterized in that the water flows at a speed of about 5-10 cm·S -1The water moves horizontally across the bottom of the aquaculture box at a speed of about 2-5 cm·s. The curved structure of the area where the bottom plate and the side of the aquaculture box meet carries the water flow vertically upward along the side of the aquaculture box, where the flow rate is generally about 2-5 cm·s -1 The conical part on the box wall close to the surface carries the water at a speed of about 0.5-2 cm·s -1 The water is directed across the surface and back toward the center of the culture tank at a rate of about 1000 rpm. A tapered sleeve on the central water pipe assists in the return of water to the floor of the culture tank. The movement of water within the culture container is circular and is fixed around the centrally located water inlet pipe. The characteristics provided by the culture container that assist in the cultivation of negatively buoyant planktonic larvae are gentle flow, minimal shear forces, and a high turnover rate of the culture container (about 0.5-1.0 turnovers per hour are achieved, thereby allowing for the maintenance of a uniform distribution of larvae and neutrally buoyant feed particles in the water column). In this regard, it will be appreciated by those skilled in the art that the present invention is particularly advantageous for aquatic animal species such as planktonic larvae that do not actually swim and prey on their food source. That is, the present invention provides an environment in which the water flow and turbulence in the culture tank are maintained in a manner that maximizes the probability that the larvae will come into physical contact (i.e., "collision") with their food source, while at the same time the turbulence and shear forces of the water flow do not cause physical damage to the very fragile larvae. In certain embodiments, the culture box is further characterized by having a set (e.g., 12) of interchangeable porous screens located around the periphery of the upper surface of the culture box to further enhance passive feeding and waste removal capabilities. These screen sets are manufactured to have a pore size range between about 2.0-6.0 mm. In yet other embodiments, the structure of the outlet end of the centrally located inlet pipe (which terminates at the base of the culture box) is designed to further ensure a smooth transition from vertical water flow to horizontal water flow while minimizing turbulence and shear forces outside the periphery of the tapered sleeve of the central water pipe. This will be described in further detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic diagram showing a RAS according to an embodiment of the present invention.

[0034] Figure 2 A schematic diagram showing a RAS according to an embodiment of the present invention.

[0035] Figure 3 A schematic diagram showing a RAS according to an embodiment of the present invention.

[0036] Figure 4 A photograph showing an embodiment of a larval rearing (or cultivation) box according to the present invention.

[0037] Figure 5A photograph showing an embodiment of a substantially centrally located water inlet tube within an embodiment of a larval rearing (or cultivation) box according to the present invention.

[0038] Figure 6 A schematic diagram showing an embodiment of a substantially centrally located water inlet pipe extending in an embodiment of a larval rearing (or cultivation) box according to the present invention.

[0039] Figure 7 A schematic diagram showing an embodiment of a substantially centrally located water inlet pipe extending in an embodiment of a larval rearing (or cultivation) box according to the present invention.

[0040] Figure 8 A schematic diagram showing an embodiment of a substantially centrally located water inlet pipe extending in an embodiment of a larval rearing (or cultivation) box according to the present invention.

[0041] Fig. 9 Shown is a top view of a 10,000 liter incubator according to one embodiment of the present invention.

[0042] Fig.10 Shown is a side view of a 10,000 liter incubator according to one embodiment of the present invention.

[0043] Fig.11 An excel spreadsheet showing water quality and conditions for various embodiments of a system according to the present invention.

[0044] Fig.12 An alternative perforated screen according to the invention is shown.

[0045] Fig.13 Interchangeable porous screens according to embodiments of the present invention are shown.

[0046] Fig.14 Interchangeable porous screens according to embodiments of the present invention are shown.

[0047] Fig.15 Interchangeable porous screens according to embodiments of the present invention are shown.

[0048] Fig.16 (A) and (B) show riser arrangements according to the invention.

[0049] Fig.17 (A) and (B) show riser arrangements according to the invention.

[0050] Fig.18 (A) and (B) show partial views of the riser of the present invention.

[0051] Fig.19 (A) and (B) show the riser ("substantially centrally located water inlet pipe (1)") arrangement of the present invention.

[0052] Fig. 20 (A) and (B) show the riser arrangement of the present invention.

[0053] Fig.21 A box design according to the invention is shown.

[0054] Fig. 22 A box design according to the invention is shown.

[0055] Fig.23 A box design according to the invention is shown.

[0056] Fig.24 A radial diffuser box plug according to the invention is shown.

[0057] Fig.25 Shown is a sleeve positioning a radial diffuser plug and attaching it to a riser arrangement.

[0058] Fig.26 Shown is a water flow diffuser at the end of a riser arrangement when a solid cone is used.

[0059] Fig. 27 A bracket design arrangement for a box according to the invention is shown.

[0060] Fig.28 A base plate design arrangement of a box according to the invention is shown.

[0061] Fig.29 An exploded view of the riser arrangement of the present invention is shown when a solid cone is used. DETAILED DESCRIPTION

[0062] RAS of the present invention is equipped with drum filter, makes it possible to remove larger organic particle waste from incubator.In an embodiment, drum filter can filter the contents of incubator at a rate of about 100-200 liters per minute or 144,000 liters-288,000 liters per 24 hours.Drum filter can be equipped with a series of filter screens (20-60 microns) of suitable size designed for use in seawater.Suitable filters for this purpose can be purchased from, for example, Fife Rui Company (France).Non-particle wastewater can then be transferred to a treatment tank, which can be a sewage tank and bubble bead filter or a biological filtration tank, for example, by gravity flow technology.Wastewater or becomes recycled water or overflow becomes waste material through remaining RAS treatment.The amount of overflow is adjusted by the input of new water minus the loss embodied in the particle treatment from drum filter or foam separator.Recycled water can be processed based on ultraviolet sterilization.This may involve single-flow or double-flow ultraviolet sterilization system. After the ultraviolet sterilization of the recycled water flow, the system can optionally include flow through one or two bubble bead filters. The filter can be used to intercept any residual particulate matter greater than about 50 μm. These filters can be obtained from, for example, AST Acquaculture Systems Technologies (USA). In a preferred embodiment, only when a sump (i.e., a non-biological filtration tank) is used in the RAS, it is necessary to use a bubble bead filter. The main reason is that the bubble bead filter can also provide biological filtration, although if used in combination with a biological filtration tank, this can provide more advantages in removing soluble waste products such as ammonia from the water flow.

[0063] The water flow of RAS according to the present invention can pass through the UV sterilizer and / or bubble bead filter to perform foam separation. Foam separators such as those obtained from Aquasonic (Australia) can be used for this purpose. The separator can further reduce dissolved organic compounds. By using a venturi device installed on the separator, ozone can be introduced at the foam separator, or ozone can be injected at a separate injection point or injected separately by using an ozone reaction chamber. Ozone can increase the redox potential of the water flow to reduce the microbial load and increase the dissolved oxygen content in the water flow. The water flow is then guided through an ozone contact chamber or a water conditioning tank. By providing enough ozone to achieve the required oxidation / reduction potential (ORP), ozonation can be performed to achieve the disinfection of recycled water. The ozone generator from the control unit adjusts the output of the generator to achieve the desired disinfection, and the ORP can be used for this purpose. New pretreated seawater can optionally be added at this time. Alternatively, new pretreated seawater can be added in the next stage, and the stage involves water passing through a degassing box (degasser). The degassing step allows for the removal of excess gases, which may include CO2, which can assist in maintaining a higher pH level in the water stream. The water stream may pass through an activated carbon filter and then a bag filter. Before the water stream enters the incubator, it may receive UV ozone destruction to ensure that the ORP is within the required range.

[0064] In an embodiment, the water flow may have the following parameters when entering the incubator:

[0065] a temperature of about 23°C-32°C, such as a temperature of about 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C or about 31°C, or a temperature in a range between any two of the above numbers;

[0066] a pH of about 7-10, such as about 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8 or about 9.9, or a pH in a range between any two of the above numbers;

[0067] Oxygen %, about 70%-140%, such as about 75%, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, 120%, 125%, 130% or about 135%, or an oxygen % in a range between any two of the above numbers;

[0068] Salinity (ppt) of about 25, 26, 28, 29, 30, 31, 32, 33, 34, 35 or 36, or a range between any two of the foregoing numbers;

[0069] ORV (mV) is about 280-450, for example, about 285, 290, 295, 300, 305, 310, 315, 320, 325, 330, 335, 340, 345, 350, 355, 360, 365, 370, 375, 380, 385, 390, 395 or about 400, or a range between any two of the above numbers;

[0070] Alkalinity (meg / L) of about 1, 1.3, 1.5, 1.7, 1.9, 2.1, 2.3, 2.5, 2.7, 2.9, 3.1, 3.3, 3.5, 3.7, 3.9 or about 4.1, or a range between any two of the above numbers;

[0071] Calcium (ppm) at about 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490 or about 500, or a range between any two of the foregoing numbers; and

[0072] Magnesium (ppm) is about 900, 930, 960, 1000, 1050, 1110, 1130, 1150, 1170, 1180, 1200, 1250, 1270, 1290, 1300, 1310, 1320, 1330, 1340 or about 1350, or a range between any two of the above numbers.

[0073] The temperature conditions listed above are best for tropical rock lobsters such as the Splendid lobster. For other non-tropical species, the optimal temperature may be lower, for example from about 18°C ​​to about 23°C.

[0074] Figure 1A RAS system according to one embodiment is shown, wherein once the water enters the sump, it is pumped and diverted through two UV sterilizers and corresponding bubble bead filters. The water flows then rejoin and enter the foam separator, where ozone can be injected through a venturi. The water overflows from the separator into an 1,800-liter ozone tank, where it is exposed to elevated ORP (oxidation / reduction potential) levels for a period of time before overflowing again into a 10,000-liter water conditioning tank. Ozonation is controlled by using an ozone generator. Water from the water conditioning tank is pumped out into the top of the deaerator and pumped into the larval tank (or incubator) through an activated carbon filter, a bag filter (100 microns), and a secondary UV ozone decomposer (ozone reduction). New water to the system enters through the deaerator.

[0075] Figure 2 A RAS system according to another embodiment is shown, wherein water flows from the breeding tank through a drum filter into a 1000-liter sump (biofilter tank), which doubles as a biofilter and contains biofilter media. The water in the sump is pumped into a foam separator through an ultraviolet sterilizer, where the water is ozonated through a venturi tube. The water overflows from the separator into a 900-liter ozone tank and then enters another 900-liter tank through a baffle to increase contact time and maintain ORP above 710 mV for 10 minutes. Ozonation is controlled by using an ozone generator. The ozonated water then flows into a 10,000-liter clean water tank (water conditioning tank), is pumped into a degasser, and is pumped into a larval tank (or incubator) through a carbon filter, a secondary ultraviolet ozone decomposer, and a bag filter (100 microns). New water to the supply system enters the clean water tank / water conditioning tank.

[0076] Figure 3 A RAS system according to another embodiment is shown, in which water from two larval tanks (incubators) flows through a drum filter and enters a 2000-liter sump (biofiltration tank), which doubles as a biofilter. The water in the sump is pumped through a UV sterilizer into a foam separator, where the water is ozonated through a venturi. The water overflows from the separator into a 1,800-liter ozone tank and then into another 1,800-liter tank through a baffle to increase contact time and maintain ORP. Ozonation is performed by a generator (water cooling). The ozonated water overflows into a 15,000-liter clean water tank (water conditioning) and then enters a 10,000-liter (water conditioning) clean water tank. The water is pumped from the second clean water tank into a deaerator, then pumped through a carbon filter and a bag filter (100 μm), split through two secondary UV ozone decomposers, and enters two larval tanks (incubators). The new water supplied to the system enters the second clean water tank (water conditioning).

[0077] To enhance the interaction between larvae and feed, all three of the aforementioned systems (i.e. Figure 1 , Figure 2 and Figure 3 ) have a pressure controlled three-way Burkert valve that diverts water back to Figure 1 of sewage and returned to Figure 2 Neutralization of clean water pool Figure 3 At the same time, the Boyd valve on the outlet of the 10,000 liter larval tank (incubator) is closed to keep the water in the tank and to keep as much water in the system as possible, essentially stopping the flow of water into the incubator for the period of time when the Boyd valve is activated. The timer that controls the Boyd valve also controls the light, turning it off when there is no water flow into the tank, to prevent larvae from gathering on the surface of the water in the tank and to cause them to sink to the bottom of the tank along with the food. A secondary UV ozone decomposer is located on all three systems just before the water enters the larval / incubator as a fail-safe measure to prevent delivery of an ORP higher than required. The secondary UV is activated by a Foxboro ORP probe placed in each larval / incubator, or can be turned on manually.

[0078] In an embodiment, the larval rearing (or cultivation) tanks described herein are based on a Kressel-type tank that provides a slow circulating water flow and has minimal internal hardware to prevent damage to the habitats by the pump or the tank itself. The tank has no sharp corners and keeps the contained animals away from the plumbing system. The water flowing into the tank creates a gentle flow that keeps the habitats suspended. The water leaves the tank through a filter that prevents the animals from being sucked into the pump inlet or overflow pipe. An example of a Kressel-type tank structure suitable for the system of the present invention is shown in FIG. Fig. 9 and Fig.10 , and has a capacity of 10,000 liters. Conventional Kressel-type flume tanks are based on much smaller volumes and are often equipped with two downflow inlets on either side of the tank that provide gravity to create two vortices in the tank. The tank of the present disclosure is specifically designed for Kressel-type flume tank systems of about 10,000 liters or more, where it is necessary to replace the water of a culture container every 24 hours.

[0079] Figure 4 A 10,000 litre tank is shown with a 50 mm central riser (referred to herein as the "substantially centrally located inlet pipe") on the tank floor, with grooved (or tapered) fixtures changing the vertical flow to horizontal flow as the riser passes through the inlet, minimising shear stress on the larvae. Due to the shape of the tank and thanks to the tapered mesh sleeves at the top and bottom of the inlet, water circulates in a circular pattern around the central riser (see Figure 5 ). Due to the tilted wings on the bladed pipe support, water also flows counterclockwise around the box ( Fig.26 Excess water flows out of the tank through 12 circumferential screens on the upper surface of the tank into the surrounding sink (see also Fig. 9 and Fig.10 ) and out the corresponding sleeved standpipe through the screens to maintain the water level and draw water evenly from all screens. The trough has a 13mm ring or built-in line with twelve 4mm 90 degree jets designed to prevent food from settling in the trough. The standpipe is fitted with a bottom slotted sleeve to allow waste water to be drawn from the floor of the trough. Water and waste food is drawn into the sleeve, through the top of the standpipe, into the ring trough and drum filter (50μm Hydrotech), and into the "cesspool". Figures 6 to 8 A variation of a substantially centrally positioned inlet pipe is shown. In some embodiments, a base plate cone is mounted at the base of the 50 mm center riser, such as Fig.11 As shown, the floor cone assists in reducing shear forces (improving the hydrodynamic quality of the incubator).

[0080] Fig.12 , Fig.13 , Fig.14 and Fig.15 An interchangeable porous filter screen is shown, located around the perimeter of the upper surface of the incubator to provide passive feed and waste removal capabilities. The filter screen assembly is manufactured to have a pore size range between about 2.0-6.0 mm. The advantage of having a variable pore size range means that the filter screen can be selected based on the growth size of the lobster larvae. The concept is that during the development of the lobster, larger feed ingredients (e.g., in the form of pellets) can be used, and thus, the larger filter screen size preferably allows any unconsumed feed to pass through without clogging the filter screen material, while still maintaining an appropriately sized animal within the 10,000 L culture container. The filter screens are preferably interchangeable to facilitate easy cleaning and maintain the required water exchange in the 10,000 liter culture container.

[0081] Fig.16 (A) shows an arrangement of a riser (referred to herein as a "substantially centrally located inlet pipe") having an inlet pipe (1) which, in use, extends above the water level of the tank (e.g. Figure 4 As shown) and terminates substantially near the bottom of the box and has an outer surface exposed to the box, wherein the upper and lower surfaces of the outer surface of the water inlet pipe are mounted with mesh-like conical sleeves (3, 4) (but the bottom sleeve 4 may be solid). When it is mesh-like, the mesh size may be in the range of about 2.0-10.0 mm.

[0082] Fig.16 (B) shows the underside of the riser, which is equipped with a radial diffuser box plug (7) located at the end of the water inlet pipe towards the base of the tank. The radial diffuser box plug secures the riser to the tank floor and ensures that the water flowing out of the centrally located pipe meets the regular water in the tank and smoothly transitions from vertical water flow to horizontal water flow while minimizing turbulence and shear forces outside the periphery of the tapered sleeve (4). It should therefore be understood that the sleeve (4) and the plug (6) work together to achieve this smooth transition. In the embodiment (see Fig.18 (b)), the radial diffuser box plug (7) can be positioned so that it extends beyond the radius of the tapered sleeve (4) by a distance of about 30-70 mm to allow water to flow out of the riser in an unimpeded manner and optimize the smooth transition from vertical water flow to horizontal water flow while minimizing turbulence at the tapered sleeve interface. By varying the degree of insertion of the riser into the bladed pipe support sleeve (10), as Fig.25 shown. Fig.24 The radial diffuser box plug is shown separated from the riser. In this embodiment, the conical sleeve (4) is solid (for example, using HDPE), and the riser (1) may also include a water diffuser (11) (in addition to the radial diffuser plug), such as Fig.26 In this embodiment, the outer chamber houses a single inlet water supply line.

[0083] Fig.18 (B) shows a partial view of a riser with a lower conical solid casing installed and equipped with a radial diffuser box plug. This figure shows an embodiment where the riser (1) includes an inner lumen (7) and an outer lumen (8). The inner lumen serves as a central source of seawater entering the box.

[0084] In certain embodiments where the conical sleeve (4) is meshed, the outer cavity houses at least 2 water supply lines to provide water flow to the outer surface of the mesh sleeve to prevent feed particle accumulation and keep the surface clean. In certain embodiments, the inner cavity hose 2, 3 or 4 water supply pipe ensures that all areas of the mesh sleeve remain free of particles. In certain embodiments, such as Fig.16 As shown in (B), the lower mesh cone (4) is fitted with an internal circular water flow tube (12) designed to spray water (under pressure) into and across the mesh to ensure that the mesh does not scale or become clogged.

[0085] Fig.19 (A) shows an arrangement where the internal and external supply lines are connected by a Y-connector. It will be appreciated that the water supply from both the inner and outer cavities of the riser terminates at the bottom of the tank.

[0086] Fig.21An embodiment of a box design is shown, characterized by having a tapered upper section on the box wall close to the surface, which has been observed to provide further advantages, namely maintaining the flow at about 0.5-2 cm·s -1 The velocity is across the surface and back toward the center of the box. Fig. 22 and 23 Another arrangement of a box design is shown having a tapered upper section with an opening to accommodate Figure 12-Figure 15 Interchangeable porous screens shown.

[0087] In order that the invention may be readily understood and implemented, certain preferred embodiments will now be described by way of the following non-limiting examples.

[0088] The disclosures of each patent, patent application, and publication cited herein are hereby incorporated herein in their entirety.

[0089] The citation of any reference document herein should not be construed as an admission that such reference document is available as "prior art" to the present application.

[0090] Throughout the specification, the purpose is to describe the preferred embodiments of the present invention, without limiting the present invention to any one embodiment or specific feature set. Therefore, it will be appreciated by those skilled in the art that, in light of this disclosure, various modifications and variations may be made to the specific embodiments illustrated without departing from the scope of the present invention. All such modifications and variations are intended to be included within the scope of the appended claims.

Claims

1. A larval rearing tank (or incubator) having a volume of about 10,000 liters or more, wherein the incubator is a substantially circular tank, characterized in that A water inlet pipe (1) is provided which is positioned substantially centrally, extends above the water level of the tank and terminates substantially near the bottom of the tank, has an outer surface exposed to the water in the tank and has an inner tube cavity (2), wherein the upper surface of the outer surface of the water inlet pipe is mounted with a conical mesh sleeve (3), which is fixed to the water inlet pipe below the surface and extends outwardly above the water level of the tank, and wherein the lower surface of the outer surface of the water inlet pipe is also mounted with a conical sleeve (4), which can be mesh or solid, fixed to the water inlet pipe below the surface and extends outwardly below the water level of the tank towards the base of the tank, wherein the inner tube cavity maintains a constant supply of seawater towards the base of the tank.

2. Tank according to claim 1, wherein the water inlet pipe (1) has an inner lumen (2) and an outer lumen (5), the outer lumen accommodating at least one water inlet supply line (6) to allow additional seawater to enter the tank from above the surface of the tank.

3. Tank according to claim 1 or 2, wherein both conical sleeves (3, 4) are mesh-like.

4. Tank according to claim 1 or 2, wherein the conical sleeve (4) is solid.

5. Tank according to any one of claims 1 to 4, wherein the centrally located water inlet pipe (1) is a standpipe and is also provided with a radial diffuser tank plug (7) at the end of the water inlet pipe towards the base of the tank.

6. A box according to any one of claims 1 to 5, wherein the radial diffuser box plug (7) fixes the riser to the bottom plate of the box and ensures that the water flowing out of the centrally located inlet pipe (1) meets the normal water in the box and smoothly transitions from vertical water flow to horizontal water flow, while minimizing turbulence and shear forces outside the periphery of the tapered sleeve (4).

7. A water circulation assembly for an aquaculture tank, the assembly comprising: An inlet pipe (1) extending above the water level of the aquaculture tank and terminating substantially near the bottom of the aquaculture tank and having an outer surface exposed to the water in the aquaculture tank and having an inner tube cavity (2), wherein the upper surface of the outer surface of the inlet pipe is mounted with a conical mesh sleeve (3), the conical mesh sleeve is fixed to the inlet pipe below the surface and extends outwardly above the water level of the aquaculture tank, wherein the lower surface of the outer surface of the inlet pipe is also mounted with a conical mesh or solid sleeve (4), the conical mesh or solid sleeve can be mesh or solid, the conical mesh or solid sleeve is fixed to the inlet pipe below the surface and extends outwardly below the water level of the aquaculture tank towards the base of the aquaculture tank.

8. A water circulation assembly according to claim 7, wherein the water inlet pipe (1) has an inner lumen (2) and an outer lumen (5), the outer lumen accommodating at least one water inlet supply line (6) to allow additional seawater to enter the aquaculture tank from above the surface of the aquaculture tank.

9. A water circulation assembly according to claim 7 or 8, wherein both of the conical sleeves (3, 4) are mesh-shaped.

10. A water circulation assembly according to claim 7 or 8, wherein the conical sleeve (4) is solid.

11. A water circulation assembly according to any one of claims 7 to 10, wherein the centrally located water inlet pipe (1) is a riser and is also provided with a radial diffuser box plug (7) located at the end of the water inlet pipe towards the base of the aquaculture tank.

12. A water circulation assembly according to any one of claims 7 to 11, wherein the radial diffuser box plug (7) fixes the riser to the bottom plate of the aquaculture tank and ensures that the water flowing out of the centrally located water inlet pipe (1) meets the regular water in the aquaculture tank and smoothly transitions from the vertical water flow to the horizontal water flow.

13. A recirculating aquaculture system (RAS), comprising: (i) Drum filters; (ii) sewage, biological filtration tanks, or bubble bead filters; (iii) at least one ultraviolet sterilizer; (iv) a foam separator with an ozone injection device or a separate ozone injection device; (v) at least one ozone contact tank or conditioning tank of a volume equal to or greater than the volume of the larval rearing tank; (vi) optionally at least one degasser; (vii) activated carbon filter; (viii) bag filters; (ix) optionally at least one secondary UV ozone decomposer; (x) at least one larval rearing tank (or incubator) according to any one of claims 1 to 6 having a volume greater than or equal to about 10,000 liters.

14. The RAS according to claim 13, characterized in that: Features (i) to (x) are in fluid contact with a stream of seawater passing through the system in the order from (i) to (x).

15. A RAS according to claim 13 or 14, wherein fresh seawater is introduced into the system at the deaerator.

16. The RAS of claim 13 or 14, wherein new seawater is introduced into the system from at least one ozone contact tank or water conditioning tank having a volume greater than or equal to about 10,000 liters.

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