TECHNICAL FIELD OF THE INVENTION

The present invention relates to a device for testing of float of feed pellets where said device comprises a tank filled with a liquid and having a water inlet. The device can be used for testing of float of feed pellets used in farming of aquatic organisms. The invention also relates to a method for carrying out such tests.

BACKGROUND OF THE INVENTION

The intensive production of marine organisms such as of fish in aquaculture is to a large extent based on the use of feed provided in form of pelleted feed compositions e.g. as compressed dry feed pellets. The quality of feed is an important issue in aquaculture, as the amount of feed needed to produce a certain amount of biomass will strongly affect the economic result in production. There are many factors affecting the efficiency of a feed such as the feed composition, its availability to the fish, the feeding rate, the assimilation of nutrients etc.

Pellets must remain stable in water until they are consumed by fish, making sure that the fish receives an adequate intake of nutrients. One aim in feed production is therefore to avoid leakage of nutrients such that the feed quality is not reduced but also to minimize the water pollution by organic load from disintegrating pellets.

Besides the feed composition also the pelleting characteristics of the feed mixtures will affect the quality of the feed. Both the composition and the physical characteristics of the feed pellet affect the floating characteristics when added to water. As many of the fish species which are commercially attractive in aquaculture production are pelagic fish, these species are feeding when the feed is distributed in the water column or close to the surface. A non-optimal sinking rate of the pellets will reduce the availability of the pellets to the fish and will thus lead to suboptimal exploitation and efficiency of the feed and finally economic losses.

The determination of the float characteristics are therefore an important issue in the determination of the quality of a feed pellet. A method to determine the flow characteristics has been described in Solomon et al. 2011 (Solomon S.G., Ataguba, G. A., Abeje, A. 2011. Water stability and floatation test of fish pellets using local starch sources and yeast (Saccahromyces cerevisae). Int. J. Latest Trends Agr. Food Sci., Vol 1 , No 1 , p. 1 -5), where the flow characteristics of pellets with different starch sources was studied. The pellets were simply suspended in a tank with water and the number of floating pellets was counted after predetermined intervals.

As standardized quantitative methods to determine the floating characteristics of feed pellets for aquaculture are lacking, it is not possible to allow a comparison between different feed types, feed batches, producers, storage conditions, water conditions etc.

Measurements carried out in field studies i.e. at aquaculture production sites not only lack accuracy, but often also reproducibility due to changing environmental conditions, as well as comparability due to non-standardized conditions.

Today's status in feed factories is that factories implement their own different internal test and quality control methods and the used methods can even differ between different lines at the factories.

Short comings in the currently applied methods in feed float testing are often related to the use of too much product on a too little surface area in the test arrangements.

Furthermore, the presentation of the pellets to the water surface is not solved in a satisfying way and this will affect the float testing. Further, the physical characteristics of the water can vary in terms of temperature, current and turbidity between different test sites.

One of the main challenges is however that most of the measurements carried out are of a qualitative nature and not of a quantitative nature. Therefore, there is a need for a new standard float test to control product quality of pellets in water.

DISCLOSURE OF THE INVENTION

Problems to be solved by the Invention

The main objective of the present invention is to develop a device and a method which allows determining the floating characteristics of feed pellets used in a liquid, especially in water, in a standardized way.

A main problem to be solved is that the device should produce reproducible results with high accuracy and comparability. The applied conditions in laboratory scale should thereby preferably resemble and simulate the typical environmental conditions found in aquaculture production such as water flow, water exchange rates etc. Another objective of the present invention is to develop quantitative methods allowing to measure in a reliable way how much feed is lost due to disintegration or early sinking after a defined period in a liquid such as in water.

Further, a test arrangement is needed being simple in handling and construction and at the same time robust and easy to maintain, allowing solving of the above mentioned challenges and providing reproducible results.

SUMMARY OF THE INVENTION

In a first aspect the present invention relates to a device for testing of float of feed pellets where said device comprises a tank filled with a liquid and having a water inlet. Said tank comprises

- a first sidewall with an overflow outlet at the upper edge of said sidewall for draining of the liquid and floating pellets,

- a second side wall of the tank which is on the opposite side of the tank in relation to said first side wall, which is provided with a first means for creating a liquid flow at or close to the upper edge which in operation creates a liquid current in an upper part of the tank between said second side wall and said first sidewall to said outlet, and that

the device comprises means for collection of the feed pellets. The advantage of this arrangement is that floating pellets can be easily distinguished from non-floating pellets and that the conditions resemble the typical conditions found in fish farming. Furthermore, the use of this test device has a high reproducibility of the results and is suitable to be used a standard device for such float tests.

The means for collection of the feed pellets are preferably downstream of the outflow.

The collections means are preferably in form of a screen. A localization of the collections means downstream of the outflow allows a simple collection and accurate determination of the floating pellets.

Preferably said means for creating a liquid flow is provided in form of a first liquid inlet. The advantage of this embodiment is that the liquid inlet can be used for both, liquid supply to the tank as well as for the creation of the liquid current.

The liquid used in the device is preferably chosen from fresh water, distilled water, sea water, and water with different salinities. By choosing water such as sea water as test liquid the typical aquaculture conditions can be resembled.

The device can comprise a second means for creating a water flow, preferably in form of a second liquid inlet, which is provided at a lower portion of the first sidewall or in close vicinity to said first sidewall creating in operation a liquid current in the lower part of said tank from said second means towards the second sidewall. Thereby, the accumulation of feed pellets on the tank bottom can be avoided, especially if combined with a liquid outlet/drain at the bottom.

The device can further comprise a feeder mounted above or in close vicinity of said second side wall for application of feed pellets, wherein the feeder preferable is a vibrating feeder. The advantage of a vibration feeder is that a constant and controlled feed addition can be achieved.

Preferably, the tank is provided with a second adjustable outlet at the bottom of the tank, whereby the outlet preferably is located in vicinity to said second sidewall. This additional outlet allows that sinking, disintegrating feed as well as the liquid can be drained out.

The tank can further comprise two rails extending from the side edges of the central overflow outlet to the sidewalls thereby providing a funnel leading the floating pellet to said central outlet. The advantage of these rails is that feed pellets are effectively guided to the overflow out let and that turbulences can be avoided which may disturb the test

arrangement.

Preferably, the first and/or second liquid inlet(s) are in form of a perforated pipe, transversally extending between parts or the whole distance of the longitudinal side walls.

In a second aspect the present invention relates to a method for testing of float of feed pellets. The method comprises the following steps:

(i) filling a test device in form of a tank comprising a liquid inlet, a first and a remote second side wall with a liquid, preferably with water,

(ii) creating a liquid current in the upper part of said tank from the second side wall to the first side wall with an overflow outlet by inflowing liquid through a liquid inlet,

(iii) adding an amount of feed pellets at or close to the liquid surface of the tank in vicinity to the second sidewall,

(iv) collecting and measuring of floating pellets that are drained out through said overflow outlet (30), and

(v) calculating the floating characteristics.

Preferably, the liquid current is adjusted such that the residence time of the pellets at the surface of the test device is regulated.

Preferably, the feed is added by a automated feeder, preferably a vibrating feeder supplied with a screen which is at least partly submerged under the liquid line.

In a preferred embodiment a liquid current is created in the lower part of said tank from said first sidewall towards said second sidewall. It is further preferred that non-floating pellets are drained through a second adjustable outlet at the bottom of said tank.

Said method can be automated and controlled by means for control and automation.

Preferably, the float characteristics of pellets determined by said method are correlated to actual floating characteristics measured at a real location, so that the actual floating characteristics can be predicted from the test method as described above.

Preferred embodiments are also described in the dependent claims.

EFFECTS OF THE INVENTION

The technical difference over prior arts is that the floating characteristics of feed pellets used in water can be determined in a standardized way, whereby the environmental conditions typically found in fish farming can be resembled.

This provides in turns several further advantageous effects such as:

- Allowance to compare different feed types, batches, feed producers, storage

conditions and environmental conditions in a reproducible way.

- The invention allows a quantitative analysis of the floating characteristics.

- The pellets can be added at the water surface in an optimal way.

High accuracy of measurements.

Possibility to determine feed losses due to disintegration or early sinking.

- The device is simple in handling and constructions and does not need sophisticated instrumentation.

- The devise is suitable for automation.

BRIEF DESCRIPTION OF THE DRAWINGS AND DIAGRAMS

The above and further features of the invention are set forth with particularity in the appended claims and together with advantages thereof will become clearer from

consideration of the following detailed description of exemplary embodiments of the invention given with reference to the accompanying drawings and diagrams.

Embodiments of the invention will now be described, by way of examples only, with reference to the following diagrams in which:

Figure 1 shows a perspective view of a device according to the present invention for float tests of feed pellets.

Figure 2 shows a perspective view of figure 1 of the longitudinal sides of the tank housing and the front side with the overflow feed collector. Figure 3 shows a side view of the device according to the present invention for testing of feed floating.

Figure 4 shows a top view of the device of figure 1.

Figure 5 shows a front view of the device of figure 1 including the overflow feed collector.

Figure 6 shows a rear view of the device of figure 1 including the upper liquid inlet and valve.

Figure 7 illustrates an embodiment of the present invention showing the device of figure 1 in operation showing the liquid flow and movements of pellets, whereby the shown embodiment has two liquid inlets.

Figure 8 shows «good» and «bad» levels for 20 feed samples measured by different methods: A) Floating test at sea having a cutoff of 1 %; B) Floating test according to the present invention with a cutoff of 5 %, C) Floating test according to the prior art with a cutoff of 1 %.

Figure 9 shows the coefficient of variation (CV) for 20 samples of different methods with 95% confidence intervals: A) Floating test at sea, B) Floating test according to the present invention, C) Floating test according to the prior art.

DETAILED SCRIPTION OF THE INVENTION

Various aspects of the disclosure are described more fully hereafter with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Based on the teachings herein one skilled in the art should appreciate that the scope of the disclosure is intended to cover any aspect of the disclosure disclosed herein, whether implemented independently of or combined with any other aspect of the disclosure. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to or other than the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim The invention will be further described in connection with exemplary embodiments which are schematically shown in the drawings, wherein Fig. 1 shows a typical embodiment of the invention.

Referring to figure 1 , a test device 1 according to the invention is shown for testing of the float of feed pellets in a liquid, preferable water, whereby said device 1 comprises a tank 10 having preferable a rectangular form with walls 14,16,18,19 at all sides and a bottom 12. In a preferred embodiment of the present invention a first and a second side wall 14 and 16 are typically but not necessarily short sidewalls, which are located remote and preferably opposite to each other in said tank 10. Sidewalls 18,19 are opposite arranged and are typically but not necessarily longitudinal side walls. The tank 10 can be open on the top

(upper side). The tank 10 is provided with an overflow outlet 30 at the upper edge of the first side wall 16 (fig. 1 and 5). The upper edge or at least a part of the upper edge of said first side wall 16 are lower than the upper edges of the remaining other side walls 14,18,19, thereby forming the overflow outlet 30. For illustrative reasons the first side wall 16 with the overflow out let 30 is also defined as the front side 16 of the tank 10. Preferably, the outlet 30 does not extend over the whole upper edge of the first side wall 16, but is provided in the middle/center of the first side wall 16 of tank 10. When said tank 10 is filled with a liquid, the liquid outlet 30 will then typically be right beneath the liquid line 62 (e.g. fig. 7). The overflow outlet 30 is used for collection of floating pellets 60. Typically, there are means for collecting of the drained feed pellets arranged downstream to this outlet or connected to the outlet (not shown). The means for collection are preferably in form of a screen, mesh, sieve, or container for collecting the floating pellets 60 for quantitative determination and straining.

The tank 10 is preferable further provided with a second liquid outlet (sink/drain) 20 at the bottom 12 of tank 10. The liquid outlets 20 is preferably located at, or close to the second side wall 14 of tank 10, which is remote to the first side 16 and which is typically a short side. For illustrative reasons this second side wall 14 of the tank 10 where the bottom outlet 20 is localized, is also defined as the back side14 of tank 10 (fig. 3 and 6).

The drain 20 is typically in form of a rectangular slit which is transversal arranged between the longitudinal side walls 18, 19 and is suitable to drain liquid and non-floating pellets 70 out of tank 10 (fig. 7). The drain 20 can be closed and regulated by a valve (not shown).

The tank 10 is provided with at least one means to create a liquid flow 40 in the upper part of the tank between the second and the first side wall towards said overflow outlet 30. Preferably, the tank 10 is further provided with a means 50 for creating a liquid flow in the bottom part of the tank from the first side wall 16 to the second side wall 14. In a particularly preferred embodiment, said means 40, 50 for creating a liquid flow are in the form of two liquid inlets (fig. 1 and 4). The first liquid inlet is thereby typically located at or in vicinity to the second side wall 14 of the tank 10 close to the top part of the tank 10 (i.e. at the liquid line 62 when the tank 10 is filled with liquid, fig. 7). The first liquid inlet 40 can be a perforated pipe 42 extending transversally at least partly between the longitudinal side walls 18, 19 of tank 10 (fig. 1 and 4). The perforations 43 are evenly distributed along the length of the pipe 42 whereby the perforations 43 are localized horizontally on that side of pipe 42 which is orienting towards the center of tank 10. The liquid can enter said tank 10 through perforations 43. If the tank 10 is filled with liquid, the inflowing liquid will create a liquid current 80 through the tank 10 in its upper part i.e. close to/along the surface of the liquid line 62 from the second side wall 14 to the first side wall 16 (fig. 7). The perforated pipe 44 is typically connected to a liquid inlet system 45 on both ends of the pipe (fig. 1 and 4). In a preferred embodiment the liquid system merges into a common pipe system 46 provided with a valve 47 for control of liquid inflow and stopping of liquid flow. Alternative liquid inlet systems instead of a perforated pipe 42 may also be used providing a similar effect of liquid inlet and preferably uniform flow of liquid along the surface or upper part of tank 10 such as a system with a number of valves, pipes etc. The first liquid inlet system is preferably adjustable and may be provided with means for external control and regulation.

Alternatively or in addition to a liquid inlet at the upper part of the sidewall 14, the tank can be equipped with other means 40 which are suitable to create a liquid flow along the surface of the tank from the second side wall 14 towards the first sidewall 16 provided that the tank 10 also has a liquid inlet such that liquid can be supplied for the functioning of the overflow outlet 30. Said means 40 can for example be a pump or other mechanical means known to the skilled person, which can create a controlled and uniform liquid flow.

On the remote side of the tank 10, which is for illustrative reasons in this context defined as the front side with the second side wall 16 of tank 10, there can be said second means 50 for creating a liquid flow. This means can be a second liquid inlet which is preferably also a perforated pipe 52 mounted at or close to the bottom 12 of tank 10 (fig. 4 and 7). The pipe 52 preferably extends along side wall 16 or along parts of the side wall 16 and can be provided with evenly distributed perforations 53 (not shown) in longitudinal direction of said pipe, whereby the perforations are oriented towards the center of the tank 10. The pipe 52 typically extends transversally between the longitudinal walls 18, 19 of tank 10. The perforations 53 in the preferred embodiment serve as said second liquid inlet to tank 10 and create a liquid current 80 along the bottom 12 of the tank from the first side wall 16 to or towards the second side wall 14 thereby passing the outlet 20 at the bottom 12 (fig. 7). As the first liquid inlet, the second liquid inlet is provided with a valve 54 for control and regulation of the liquid inlet and current 80. The valve 54 can be provided with a handle 55 for control and regulation (see e.g. Fig. 2, 3, 5, and 6) or may be equipped with means for regulation and control which allow an automated regulation of said valve and liquid current. The second liquid inlet is not restricted to a perforated pipe. Alternative liquid inlet systems may also be used providing a similar effect of a preferably uniform liquid flow along the lower part of the tank 10 such as a system with a number of valves, pipes etc. Alternatively to a liquid inlet system for creation of the liquid flow along the tank bottom, other known means for creating a liquid flow may be used such as a circulation pump.

The unique form and location of the first and second means 40, 50 for creating a liquid flow, which are preferably provided in form of a first and second liquid inlet according to the present invention thus create in test operation a liquid current 80 along the bottom 12 from the first side wall 16 towards or to the second side wall 14 (fig. 7), passing the liquid outlet 20 at the bottom 12 where any non-floating pellets 70 can be drained out if the drain 20 is open. Due to the first liquid inlet (or said alternative first means for creating a liquid flow) at the top of the second side wall 14, the flow changes direction at the second side wall 14 and proceeds along the liquid surface (i.e. in the upper part of tank 10) towards the second outlet 30 of the tank located at the upper edge of the first side wall 16. Floating pellets 60 are thereby drained out of tank 10 and can subsequently be collected for quantification (fig. 7). The forced liquid as indicated in figure 7, thus ensures an even surface flow over the edge of the tank 10 at the overflow outlet 30. Furthermore, it ensures that non- floating pellets 70 can be drained out as they are directed over the edge of the liquid outlet 20 at the bottom 12 of tank 10, and the bottom 12 is cleaned from pellets. In an embodiment having only the first liquid inlet 40 (or first means fro creating a liquid flow) in the upper part without a liquid flow at the bottom, non-floating pellets 70 will accumulate at the bottom 12.

Preferably, the tank 10 further comprises two thin rails 32,33 mounted on each of the sides of the liquid outlet 30 (Fig. 1 and 4). Each of the rails 32,33 extends diagonally sideways to the respective, preferably longitudinal, side walls 18 or 19, where they are attached to the walls. Thereby the rails 32,33 provide a funnel for the liquid current along the surface and lead the floating pellets along the liquid surface to the central overflow outlet 30 for collection. The rails can be thin in their vertical dimension just extending beneath the liquid line. Another function of the rails is to avoid turbulence in the current.

The tank 10 is typically provided with a feeder 90, which preferably applies a steady stream of pellets to the surface of the test tank (not shown) at or close to the second side wall 14 of the tank. The feeder 90 is thereby typically mounted above the tank in vicinity to the backside of the tank. In a preferred embodiment feeder 90 is chosen from a vibrating feeder which allows applying a slow and steady stream of pellets to the surface. The feeder output can be regulated vertically and horizontally. Preferably, a screen is attached to the vibrating feeder which is at least partially submerged under the liquid line 62, when said tank 10 is filled with liquid to achieve a gentle application of the pellets to the surface.

Alternatively, other feeders known to the skilled person may be used such as belt feeders, screw feeders, batch feeders etc. The feed may also be added by manual methods as from a mesh screen, by hand etc. Preferably, means for adding the pellets to the liquid surface shall allow a gentle addition to the liquid surface. It is an advantage if the pellets meet the liquid surface with a small force to allow the surface tension to act over the pellet. This improves the reproducibility of the measurements and contributes to an extenuation between individual pellets differences. It is preferred that said feeder is combined with a submerged or partly submerged screen for addition of the pellets to the tank.

An embodiment of the present invention relates to a device (1) for testing of float of feed pellets where said device comprises a tank (10) with sidewalls, wherein

- one of the tanks (10) sidewalls (16) has a overflow outlet (30) at the upper edge of said sidewall (i.e. located right beneath the waterline in water filled stage) for draining of water and floating pellets (60), which are thereafter collected by means for collection,

- a second side wall (14) of the tank which is on the opposite side of the tank in relation to the side wall (16), is provided with a water inlet at or close to the upper edge of the side wall

(14) which in operation creates a water current (80) in an upper part of water in the tank from said sidewall (14) in longitudinal direction to the sidewall (16) comprising the overflow outlet (30). A method for testing of float characteristics of feed pellets can comprise the following steps:

(i) filling a test device in form of a tank with a liquid, preferable water,

(ii) creating a current in the upper part of the liquid in said tank in longitudinal direction of the tank towards an overflow outlet (30) by inflowing water through a water inlet,

(iii) adding an amount of feed pellets to the surface of the tank in vicinity to sidewall (14) and the water inlet and

(iv) collecting of the floating pellets (60) that have been transported by the current and are drained out through said overflow outlet (30), and calculating the floating characteristics.

In a preferred embodiment; typical dimensions of the test device 1 (i.e. housing/tank) are e.g. 150 cm as length, 75 cm in width and 20 cm in height. Smaller dimensions can be used in order to conserve liquid and space. Typical suitable dimensions would then be a length of e.g. 50 cm, a width of 40 cm and a height of 20 cm. The feeding screen is typically 10 cm x 15 cm.

The tank 10 can be made of any suitable material(s), which is sufficient stable and inert in the used liquid such as fiber glass, metal, preferably stainless steel, glass, synthetic materials and any combinations thereof.

In the context of the present invention the expression "water" should be interpreted to include fresh water, distilled water, sea water, water with different salinities and any other water-based liquid.

In the context of the present invention the expression "liquid" should be interpreted to include "water" as defined above, but can also include other suitable liquids such as oil(s) and oil-based liquids as well as mixtures of different liquids such as of oil and water.

Preferably, the testing is however carried out in water, most preferred in fresh water, distilled water, sea water or water with different salinities.

It will be appreciated that the features of the invention described in the foregoing can be modified without departing from the scope of the invention.

Float test procedure manual:

A non-automated float test procedure using the device of the present invention .g. be performed by carrying out the following subsequent steps:

1. Filling the tank to overflow with liquid, preferably with water, whereby the bottom outlet 20 is closed

2. Weighing of test feed, e.g. 100 grams

3. Adding feed to feeder 90

4. Start and regulate liquid flow (valve 47,54)

5. Start feeder 90

6. Collect feed pellets, which have passed through liquid outlet 30 and were collected on screen after predefined period, e.g. after 1.5 minutes from start of feeder

7. Reweigh samples collected on screen. The weight of the samples can preferably be compared with a control sample with a defined amount of feed which is exposed to water for the same time.

8. Determination of floating pellets

9. Drain out liquid/water and pellets from tank, e.g. for 10 seconds

10. Optionally run next sample The device is suitable for automated operation if supplied with corresponding electronic regulation and control systems (not shown). The control system initiates opening of one or more of the inlet valves, and closes the valve on the bottom, then the tank is filled with liquid. A sensor monitors the filling of the tank, and sends a signal to the controller when the tank is filled. The bottom valve is opened, and the flow of liquid is controlled to obtain an even liquid movement speed across the tank surface. An automatic feeder feeds one of the test feed samples, and the sample is allowed to move on the tank surface for a predetermined time period, for instance 90 seconds. Thereafter, the feed samples that have been collected via the overflow outlet 30 are weighted, and the control unit calculates the percentage of feed particles that have floated to the outlet 30. It is possible to automatically test the same feed sample at different time periods to determine the floating characteristics of the feed sample.

A number of variations on the above can be envisaged. For instance it is desirable to only measure the disintegration or sinking of pellets under standardised conditions. In this case pellets may only be removed via the bottom outlet 20 and collected thereafter by suitable means for collection such as a screen, container, mesh etc. In this case the overflow outlet may optionally be closed by suitable means such that floating pellets are not drained out there. Such an arrangement can for example be useful if the effect of environmental parameters on the pellets sinking or disintegration is to be studied. The disintegration and/or sinking may then be determined in defined intervals for example depending on the water flow. The sinking/disintegration of pellets may also be studied in addition to the floating if pellets on the bottom or in the bottom sink/outlet are drained out through the bottom outlet and collected by suitable means such as a screen and subsequently measured and /or analysed.

Standardization of test method

A standardization of the test methods producing reproducible results also between different test units and feeds affords that the test device will be standardized and that the test conditions applied are identical/comparable. Several features can be controlled, tested and monitored:

the average retention time of the feed samples

the amount of feed samples

the wet properties of the feed samples

- the feed rate and how the feed is applied to the liquid the temperature and/or salinity of the liquid in the tank

EXPERIMENTAL SECTION Experiment 1 : Floating test

The method according to the invention was tested and evaluated with comparison to a real life test, i.e. the floating characteristics of a pellet in salt water, i.e. the sea. This is a measure of the quality of the pellets. If the float is over an agreed upon value the customer may complain. A good and a bad quality parameter were determined for 20 different feeds (5 mm and 3 mm).

Test Methods used

1. The float at the sea was determined by counting 100 pellets, throwing the pellets on the surface of the water, waiting 10 seconds before counting the pellets floating to get a percent float. This procedure was repeated 3 times. The location where the test was carried out had a 3% NaCI content, a calm surface, and a temperature of about

14 °C. Anything above 1 % float was considered as "bad" and below 1 % float was considered "good".

2. A method according to the prior art was used as a reference, and was as following:

100 pellets were dropped from a constant height in a repeatable way into 8% NaCI at a known temperature, then the pellets were counted to get a percent of floating pellets. This procedure was repeated 3 times. Anything above 1 % float was considered "bad" and below 1 % float was considered as "good".

3. The floating test according to the invention was done as follows:

a. A vibratory feeder placed above the water stream was set up with an inclined metal mesh 20 cm wide at a 30 degree angle, 34 cm long. The edge of the metal mesh contacted the water surface 30 cm from the discharge end. The water flow was 15 l/min with a temperature of 9 °C and a 5% NaCI concentration.

b. 100 g of pellets were added to the feeder and the feeder was started. The floating pellets were collected in a mesh screen and reweighed after waiting 1.5 minutes. Then the percent float was calculated. This was repeated 3 times. Anything above

5% was bad and below 5% was good.

Results

When compared to the sea test the method according to the prior art only identified 50% of the feeds correctly while the new float test identified 80% correctly (figure 8). The float test according to the invention was also more sensitive to feed difference as noted by the 5% cutoff while the method according to the prior art had much less sensitivity. The float test according to the invention allows a more sensitive method, and can be automated easily. Each method had high coefficients of variation but the new float test was lower than the others (figure 9).

INDUSTRIAL APPLICABILITY

The invention according to the application finds use in industrial production of feed pellets for aquatic organisms such as farmed fish, whereby the device and method can for example be used by the feed producer as well as at the location where the feed is used.