Low-Cost Automated Feeder for Fry and Fingerlings


U.S. Fish and Wildlife Service
Southeastern Fish Cultural Laboratory
Route 3, Box 86
Marion, Alabama 36756, USA

' Present address: Texas Cooperative Fish and Wildlife Research Unit, Texas Tech University, Lubbock Texas 79409, USA.


Abstract.—An electrically operated automatic feeder has been used to reliably deliver dry feeds to fry and fingerlings of striped bass (Morone saxatilis). Quantities of starter ration from 4.6 to 114 g per cycle of feeder activation were delivered with 98-99% accuracy in 10 repetitive trials. Pellets of 0.24-0.32 cm were delivered with 93-96% accuracy in 10 trials. The feeders were constructed with commonly available shop tools at a cost of about US$38, and the controllers cost about $90 for materials. Details for construction of the feeder and timer control circuit are provided.


Fish feed is the single most important component in the production of large fish for recreational programs and for the commercial food industry. However, the cost of feed for fry and small fingerlings is usually rather unimportant as compared with other costs, such as maintenance of brood stock, spawn taking, and hatchery operation. Because both the quantity and cost of starter rations required by commercial fish farms and governmental hatcheries are rather low, little effort has been devoted to the development of automated feeders that will reliably deliver measured amounts of feeds for fry and small fingerlings.

Several investigators have reported on the benefits of multiple feedings (Greenland and Gill 1979; Noeske-Hallin et al. 1985) or timed feedings with automated and on-demand feeders (Statler 1982). Others have modified or developed feeders for fry diets (Falls 1980; Winfree and Stickney 1981; Charlon and Bergot 1986), for use with Oregon moist pellets (Pozar 1980), or for use above cages (Meriwether 1986) or raceways (Schweinforth et al. 1984). A review of existing feeders indicated that many would perform well with the feeds and in the application for which they were designed but would not operate satisfactorily when used to feed starter rations at selected times to striped bass (Morone saxatilis) in ponds. For example, feeders designed to deliver pelleted rations often failed to operate when filled with starter feeds. The high oil content in these crumbled formulations makes them adhesive and causes the feed particles to bridge over the outlet port of most feeders. My objective was to develop a feeder that would reliably deliver predetermined quantities of starter rations 1-48 times/day and would operate reliably over outdoor tanks, ponds, and raceways. An additional requirement was that the feeder perform with little maintenance, even when exposed to adverse weather.

The feeder was constructed of a 19-L bucket used as a feed hopper, an inverted traffic cone, a small 12-revolution/min gearhead motor, and miscellaneous hardware (Table 1; Figures 1-3). Caution. Buckets previously used to store herbicides or pesticides should not be used as feed hoppers. Any steel container should be thoroughly cleaned and painted inside and outside to reduce corrosion by moisture and salts in the feed. The traffic cone should be soaked in clean water for several days to leach out toxic plasticizers.

The timed controller consisted of a 15-min interval clock timer, a time-delay relay, a rain-tight mounting box, and miscellaneous hardware. The cost of components for a single feeder in June 1987 was about US$38, and the cost of the controller unit was about $90. The tools and construction skills required were those commonly found in farm and hatchery maintenance shops.

An 18-cm-diameter hole cut in the bottom of the bucket was centered over the wide end of the traffic cone. The base of the plastic traffic cone was trimmed to fit the bottom of the bucket and sandwiched between the bottom and a steel ring (Figure 2). Holes large enough to accept the 0.32cm-diameter steel rod were drilled into the center of the two polyvinyl chloride (PVC) plastic disks (Figure 3). Two curved slots, about 1.1 cm wide and 3.5 cm long were cut into the smaller PVC disk, and matching slots were cut into the larger PVC disk. After the small disk and large disk were clamped together to maintain alignment of the curved slots, two holes were drilled next to the edge of the small disk and into the larger disk. Holes in the small disk were threaded to accept machine screws and used to mount the two PVC disks on the small end of the traffic cone. Once the disks were mounted on the end of the cone, the small disk inside the cone and the large disk outside, the holes were checked for alignment and trimmed to ensure clear passage for the feed.

TABLE 1.—List of materials required to construct the lid, feeder, and controller for the automated feeder. Item numbers correspond to those in Figures 2-4; cost is as of June 1987.

Number          Description                                                                                                Cost (US $)

1                      Plywood disk, 30 cm diameter, 1.6 cm thick                                           $ 0.60
2                      Rubber strip, 35 cm long, 5 cm wide, 0.16 cm thick                               $ 0.10
                        Miscellaneous:   wooden blocks, nails                                                   $ 0.50

3                      Bucket, 19 L                                                                                                $ 0.50
4                      Motor, 12 revolutions/min, 115 V AC                                                     $ 22.17
                            (Dayton Model 2Z807a)                   
5                      Steel bar, 33 cm long, 5 cm wide, 0.32 cm thick                                      $ 0.27
6                      Polyvinyl chloride (PVC) rod, 2.5 cm diameter, 4.8 cm long                $ 0.26
7                       Steel rod, 0.95 cm diameter, 72 cm long                                                   $ 0.28
8                       Brass welding rod, 0.32 diameter, 30 cm long                                         $ 0.10
9                       Steel ring, 27 cm outside diameter, 19 cm inside diameter,                    $ 0.50
                       0.075 cm thick
10                     Plastic traffic cone, 43 cm tall (Direct Safety model N 12-157b            $ 6.50
11                     Brass welding rod, 0.32 cm diameter, 15 cm long                                   $ 0.05
12                     Brass welding rod, 0.32 cm diameter, 8 cm long                                     $ 0.03
13                     PVC disk, 16.8 diameter 0.64 cm thick                                                      $ 0.87
14                     PVC rod, 7.6 cm diameter, 2.5 cm long                                                     $ 1.22
15                     Plasic pipe, 15 cm inside diameter, 7.6 cm long                                      $ 2.02
16                     Brass welding rod, 0.32 cm diameter, 8.4 cm long                                 $ 0.03
17                     Power cord, 115 V, 2 m long                                                                     $ 1.52
18                     PVC disk, 5 cm diameter, 0.64 cm thick                                                   $ 0.10
                Miscellaneous:   nuts, bolts, washers, grommets, PVC glue,
                         paint, elastomeric silicone sealant

19                     Rain-tight box, 30 x 30 x 15 cm (Hoffmanc)                                             $ 27.77
20                     Back plate (Hoffman part A-12N12P)                                                      $ 3.94
21                     Timer, 15-min interval clock (Dayton model 2A517)                             $ 23.03
22                     Relay, time-delay, 1.8-180 s (Dayton model 6X604C)                           $ 27.19
23                     Socket, 8-pin octagonal (Dayton model 5X852)                                    $ 2.22
24                     Socket, lamp, 115 V, porcelain, flat mount                                              $ 1.54
25                     Lamp, 15 W, 115 V                                                                                     $ 1.25
26                     Receptacle, duplex, 115 V with cover                                                     $ 1.03
27                     Grommet                                                                                                      $ 0.10
28                     Power cord, 14-3, 115 V, 2 m long                                                            $ 1.52
                Mescellaneous:   nuts, bolts, wire, wire terminals, cable ties               $ 1.00

TOTAL COST                                                                                                                    $ 129.21

a Dayton Manufacturing Company, Chicago, Illinois.
b Direct Safety Company, Phoenix, Arizona.
c Hoffman Engineering Company, Anoka, Minnesota.

FIGURE 1.—Placement of the automatic feeder over a small pond. The simple bracket supporting the feeder is mounted on the face of the concrete drain structure.

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The motor was mounted in the upper portion of the bucket on a bracket made from the steel bar (Figure 2). Three holes sized to accept the brass welding rods were drilled 14, 45, and 59 cm from one end of the steel rod. A 30-cm piece of welding rod was passed through the upper hole, a 15-cm piece through the middle hole, and an 8-cm piece through the bottom hole. The brass rods were centered in the hole and locked in place by using a punch and hammer to distort the holes in the steel rod. Ends of the welding rods were gently curved to insure that they did not bind against the sides of the bucket or cone (Figure 2).

The 0.95-cm-diameter steel rod was attached to the motor by a coupling made from the PVC rod and drilled to accept the steel rod on one end and the 0.70-cm-diameter motor shaft on the other. Holes were drilled and tapped to accept set screw used to lock the coupling to the motor shaft and the steel rod. The 7.6-cm-diameter PVC rod was drilled to slide on the lower end of the steel rod. The upper portion of this PVC rod served as a stop plate to prevent flow of feed from the feeder when the motor was not running. The lower 2 cm of the 7.6-cm-diameter rod can be milled down to about 4 cm diameter and drilled to accept a setscrew used to lock the stop plate in place.

The 15-cm-diameter PVC pipe was glued to the bottom of the large PVC disk to provide a rain tight shield (Figure 3). A hole drilled into the PVC pipe about 2 cm below the upper edge was used to mount a brass bar that scraped feed from the stop plate. Elastomeric silicone was used to seal all penetrations and screw holes to prevent rain from entering the feeder.

A lid (Figure 1) was constructed of plywood, and four wooden blocks were arranged to keep the lid centered over the bucket. A rain skirt was attached to the edge of the lid and fitted to lap over the upper edge of the bucket. A small metal handle on the lid and a coat of paint on the lid and bucket provided the finishing touches.


FIGURE 2.—Relative placement of parts for construction of the feeder: (1) plywood disk, (2) rubber strip, (3) bucket, (4) motor, (5) steel bar, (6) polyvinyl chloride (PVC) rod, (7) steel rod, (8) brass welding rod, (9) steel-ring, (10) plastic traffic cone, (11) brass welding rod, (12) brass welding rod, (13) PVC disk, (14) PVC rod, (15) plastic pipe, (17) power cord. Item numbers correspond to those in Table 1. (Drawing not to scale.)

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FIGURE 3.—Exploded view of the lower section of the feeder: (10) plastic traffic cone, (12) brass welding rod, (13) polyvinyl chloride (PVC) disk, (14) PVC rod, (15) plastic pipe, (16) brass welding rod, (18) PVC disk. Item numbers correspond to those in Table 1. (Drawing not to scale.)


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The controller consisted of a 15-min interval timer, a time-delay relay mounted in a socket, a 15-W lamp mounted in a porcelain socket, and a duplex receptacle (Figure 4). The connecting bus on each side of the duplex receptacle was cut so that one receptacle could be controlled by time-delay relay 1 and the other by time-delay relay 2. Components of the controller were arranged on the back plate of the rain-tight box. Figure 4 shows placement of two sockets for two time-delay relays. Multiple relays can be operated by a single 15-min interval timer and used to control multiple feeders. Components were wired as shown in Figure 5.

The 15-min interval timer controls the time of day when the feeder is activated. It can be operated a maximum of twice per hour (two periods of 15 min on and 15 min off) or as infrequently as once every 24 hours. The clock motor of the interval timer closes the normally open contacts of the switch, which in turn energizes the coils of the time-delay relays (Figure 5). An adjustable dial on the top of each relay controls the duration of closure of the normally open contacts in the relay that provide power to the female plug of the duplex receptacle. The male plug transfers power to the feeder motors. The 15-W lamp keeps condensation from collecting inside the control box and helps prolong service life of the electrical components. Caution. To insure safe operation, the electrical power for this unit, like that for any electrical device used around fish tanks and in wet environments, should be provided only through an electrical circuit with ground-fault-interrupt protection.

The quantity of feed delivered per activation cycle is controlled by adjusting the dials of the time-delay relays. Multiple relays allow the quantity of feed delivered from multiple feeders to be individually adjusted. A 3- to 300-s-interval time-delay relay (model 6X605C, Dayton Manufacturing Company) can be used in place of the 1.8to 180-s relay (model 6X604C) if a larger quantity of feed is needed per activation cycle.

The stop plate can be adjusted up or down to deliver finer or larger feed particles, respectively. The feeder has been used to deliver feeds as fine as starter rations and pellets as large as 0.64 cm in diameter. The motor turns the steel rod and the brass welding rods to break up the feed and prevent it from bridging over the delivery ports. To insure delivery of oily and sticky feed, I attached a plastic cable tie to the brass welding rod in the lower end of the cone, which serves as a brush to sweep feed particles through the delivery ports.


FIGURE 4.—Interior view of the control box: (19) rain-tight box, (20) back plate, (21) timer, (23) 8-pin socket, (24) lamp socket, (25) lamp, (26) receptacle, (27) grommet. Item numbers correspond to those in Table 1. (Drawing not to scale.)

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FIGURE 5.—Schematic diagram of the components in the control box, showing the electrical connections for the lamp (L), clock motor (CM), power switch (SWI), parallel time-delay relays (TDRI, TDR2), female plugs (FP) of the receptacle, and male plugs (MP) for the motors in the feeders (FMI, FM2).fig5.gif (6609 bytes)


TABLE 2.—Average weights of feed delivered by the automatic feeder and coefficients of variation (CV = 100SD/ mean) in 10 replicate tests involving six diets, four settings of the stop plate, and eight feed delivery times set by the time-delay relay.

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This type of feeder has been in operation on over 40 ponds for about 4 years at the Southeastern Fish Cultural Laboratory and has worked reliably throughout the year to deliver feed to striped bass fry and fingerlings. A series of tests was conducted in the laboratory to evaluate its reliability to deliver feed at various settings. The feeders were tested in a factorial design involving six sizes of feed, four settings of the stop plate, and eight settings of the time-delay relays. Ten serial replicates were conducted at each of the settings. The coefficient of variation about the average quantity of feed delivered in a 10-replicate series was used to establish repeatability of performance (Table 2).

Salmon starter ration number 1 could be delivered at 4.6 g per cycle with a 2% error; 7.2-114.1 g could be delivered at time settings of 15-240 s with an error of only 1 %. The coefficient of variation increased as the stop plate setting increased but decreased as the duration of feed delivery increased.

The delivery of salmon starter number 2 was somewhat more erratic than that of the smaller number 1 diet. The optimum stop plate settings appeared to be 0.6 and 1.3 cm for delivery of 5.5-36.6 g of feed. The coefficient of variation increased at delivery times of 240 s, when the quantity of feed delivered per cycle was greater than 83 g.

With the proper setting of the stop plate and adjustment of the time of operation, the unit would reliably deliver, with a 4-6% error, 4.5-682 g of 0.24-cm pellets. Pellets of 0.32 cm were delivered at rates of 52.2-529 g per cycle with a 4-7% error. The coefficient of variation ranged from 28 to 190% for delivery of 0.4-cm pellets and from 5 to 100% for delivery of 0.64-cm pellets. Flow of the larger size pellets from the feeder was limited by the size (1.1 x 3.5 cm) of the slots cut into the PVC disk at the base of the cone (Figure 3). It appears that the width of these slots should be at least three times the diameter of the pellets to be delivered to minimize error.

Acknowledgments.—I thank H. K. Dupree, U.S. Fish and Wildlife Service, Stuttgart, Arkansas, and L. C. Woods, Baltimore Gas and Electric Company, Crane Aquaculture Facility, Baltimore, Maryland, for critically reviewing the manuscript and making helpful suggestions.