Growing Mealworms as a Fish Feed for Sustainable Aquaponics

WORK ACTIVITIES IN 2016 

Mealworms were purchased and containers were modified to grow them in March of 2016.  The containers were recycled from food grade bins obtained from local restaurants.

Both 2-inch deep (shorter) and 5-inch deep (taller) sizes were modified by cutting rectangular openings in 2 places on each lid and gluing screen door mesh to these openings. 

The openings were positioned so that bins could be stacked in a perpendicular manner on top of each other and allow for adequate ventilation of each container. (See attached photos) 

Initially 4 cups of substrate materials were placed in each of the two different sized containers with 300 meal worms in each container.

A subsequent set of four taller containers with 8 cups of substrate materials and 600 worms in each were started two weeks later.

Additional substrate materials and pieces of produce for moisture were added on approximately biweekly basis, as needed. Ratings were taken to evaluate estimated number of mealworms and activity, as well as depletion of substrate and moisture containing organic produce items.

Data loggers were added to existing ones and some were moved to track temperatures in greenhouses, soil, air, plant root zones, fish tanks and mealworm growing trays.

After about 3 months, it was determined that the shorter bins, although adequate for growth were less desirable than the taller ones.  Even though the substrate volume was reduced significantly from feeding by mealworms resulting in reduced dust sized particles, the taller bins would allow for more room for longer term growth.  Also, temperatures were likely to fluctuate more with the reduced air space above the growing media and drying was greater due to closer proximity to the screen openings in the lids of the shorter bins.  Therefore, the mealworms were all shifted into larger containers after this initial phase of evaluations.

Four different certified organic materials were evaluated as substrate media.  These were selected based on local availability and pricing and included rolled oats, rye flakes, spelt and red wheat bran.  A local organic bakery was the source for the rolled oats and spelt.  A local Whole Foods store was the source for rye flakes and red wheat bran.

Initial growth and maturation into adult beetles was slightly better for rye flakes.  However, both the spelt and wheat bran showed better feeding and more mealworms after several months than the rye flakes and rolled oats.  When sufficient quantities of adult beetles were observed, these were moved into a separate bin. The ones from the rolled oats and rye flakes were moved into a bin with a combination of both rolled oats and rye flakes.  The adults from the wheat bran and spelt were moved into separate containers with the same substrates that they were originally growing in.

After 4 months of evaluations, it was determined that the spelt and wheat bran had the best feeding and growth rates.  The rolled oats and rye flakes were not consumed as completely and the residual material was not small enough to allow for screening out of the mealworms to harvest for feeding to the fish.

The numbers and feeding activity observed was similar for both the spelt and wheat bran. Since the price was significantly higher for the spelt at more than double that for wheat bran and the growth rate was similar, after 6 months of evaluations, it was decided to focus on growing methods for maximizing production using the wheat bran alone.

Initial plans were for building a shaded containment area to grow the mealworms in the passive solar high tunnel greenhouse.  However, after initial observations of temperature fluctuations, especially air temperature spikes reaching over 100 degrees F, it was decided that use of a shaded room in the cooler renewable energy greenhouse would be more reasonable for the initial evaluations.  Plans will allow for increasing the supply of mealworms this spring and number of bins to the point where some bins will be moved to shaded containment in the passive solar greenhouse for further evaluation this summer.

The renewable energy greenhouse has supplemental propane heating and is set to keep temperatures above 45 degrees during winter months, however, temperatures as low as 40 degrees were recorded in the mealworm growing bins, as this room was far enough from the supplemental heat source to allow for lower temperatures during extreme colder nights.  It was observed that as temperatures dropped below 50 degrees, mealworm activity and growth was slowed significantly.  When temperatures dropped below 45 degrees, this resulted in the death of most of the adult beetles.  Until that time, no significant odors were observed from the growing bins. The dead adult beetles were not removed in the hopes that they might revive, but subsequent rotten smell proved that was not the case.  The activity of mealworms was only slowed at lower temperatures.  Some of the initially purchased mealworm larvae were even placed in the freezer for several days then thawed out without any loss of worms to determine if freezing temperatures would be an issue in the unheated passive greenhouse.

It was observed that during hotter summer days that the need for supplemental moisture was critical for growth.  Several different sources were evaluated, including potatoes, carrots, cucumbers, summer squash and apples.

Initially potatoes and carrot pieces were placed in shallow plastic container lids that allowed mealworms to easily access, since the raised edges of the lids were low enough to not discourage any climbing over them. 

Even with the shorter food bins, little to no climbing up the walls was observed.  Potatoes had a greater feeding rate than the carrots.  As they became available during the summer months both cucumbers and summer squash were evaluated as a source of water for the mealworms.

Cucumbers were favored and devoured at a quicker rate than other items.  However, subsequent screening to separate mealworms resulted in cucumber seeds needing to be picked out from screened mealworms.  Also, infestations of cucumber beetles limited availability of cucumbers and summer squash during the late summer months.  Apples were then evaluated.  The mealworms devoured these for the moisture at rates similar, but slightly slower than cucumbers, however, they did not digest the skins and these had to be removed as mold was observed growing on the remaining skins.  Also, fruit flies were small enough to allow them to multiply, as the screening material hole size was large enough to allow them to lay eggs on the apples.

It was also observed that slices about ¼ inch thick were the optimal size to allow for greatest surface area access by mealworms, as opposed to irregular sized pieces.

During the dryer summer months, consideration was also given to adding water to separate lids, however, due to concerns about encouraging mold growth in the substrate and the need to carefully add water on an almost daily basis due to evaporation, it was decided to continue to add pieces of produce items.

The moisture at times during the hottest summer months was seen as the limiting factor.  A miniature water bowl with some kind of float mechanism that would prevent any overflow getting mixed with the growing substrate would be ideal, but due to the bowl needing to be shallow enough to prevent the mealworms from drowning, the design would be a challenge. It may be possible use a sponge in a shallow tray, but automated watering may be difficult to match with consumption rates.  Since no such device has been located, pieces of potatoes and seedless cucumbers (as available) will continue to be the source of moisture for the mealworms moving forward, until another alternative delivery method is developed.

Labor activities for growing mealworms included container construction, adding substrate materials, providing sliced produce items to allow for sufficient moisture to encourage growth, separating out adults, recording temperature data, making observations and sample analyses.  More time than expected was spent separating out and moving adult beetles so that they would not feed on young larvae.  Screening before larvae are too large may be an option to minimize the amount of time for separating.

Nutrient analyses of the fish feed, Aquamax 400, and mealworms grown on wheat bran were completed in December.  Prior to analysis, the fresh weight versus dried weight of the mealworms was determined to be able to provide an adequate size sampling of fresh mealworms for laboratory analysis.

RESULTS AND WHAT WAS LEARNED DURING 2016

• Mealworms were successfully grown in food grade bins recycled from restaurants that were modified with ventilation screening in the lids. The taller containers were more suitable for accommodating longer term increase of substrate materials.

• Wheat bran was determined to provide the most growth activity and to be the most cost effective organic substrate material that also allowed for an easy screening process to harvest mealworms when needed.

• Moisture availability is critical during hot summer months for mealworm growth. Cucumber slices were the preferred means for providing moisture for mealworm growth, however, seedless varieties will be grown next year to avoid seeds during the screening process. Potato slices were also suitable for use when supplies of fresh items grown on-site are limited and are currently a low cost option.

• Temperature ranges fluctuated more in the unheated passive greenhouse than in the main renewable energy greenhouse. The fish tank, located in the passive greenhouse, had temperatures similar to ground temperatures as they are 50% in-ground.  In spite of air temperatures as low as 0 degrees F this winter, the covered frames above the fish tanks prevented freezing of circulating water and plant materials and harvests were able to continue through the winter months.

• Temperatures below 45 degrees resulted in the death of mealworm adult beetles, but did not result in any dead larvae mealworms, however, slower growth and activity were observed at low temperatures and reduced yields of mealwoms are expected. This should not be a problem, as fish feeding is stopped whenever water temperatures drop below 50 degrees, which is generally from late November thru early February.  Quantities needing to be grown during summer months will need to be determined to have a sufficient amount for fish feeding.  Since freezing of mealworms appears to be a viable option for maintaining a reliable source of mealworms when thawed, over producing during summer months can provide adequate supplies for months when growth is slower than fish feeding rates.

• The dried weight of mealworms was determined to be 40% of the fresh weight. Dried weights sample analyses were virtually identical for the crude protein content of the fish feed and the mealworms. This means that to get the equivalent nutrients as from 1 lb of dried fish feed, 2.5 lbs of fresh meal worms will be needed.

• Significant amounts of mealworms will be required during the second phase of this project to provide adequate quantities for feeding the fish and more containers will be stocked with mealworms and wheat bran in late winter/early spring of 2017.

Dry weight analysis:

WORK PLAN FOR 2017

• The quantities of mealworms will need to be increased significantly to provide adequate amounts for the feeding phase. This will be accomplished prior to initiation of fish feeding as water temperatures increase above 52 degrees, usually in late April or early May. Quantities of mealworms were increased prior to the spring of 2017.  However, due to heavier than expected consumption rates, the quantities raised were not sufficient to complete the test and additional mealworms were ordered three times during the 2017 grow out period.

• Separate bins will be evaluated to determine Feed Conversion Ratio for yield of mealworm protein per pound of wheat bran over a six month period to be able to extrapolate potential economic feasibility for growing fish feed as compared to purchasing commercial feed. See discussion of results for 2017.

• Plant growing bins will be emptied with new growing media and new plantings by early March. Based on market demands for the coming season, the planting ratio will be approximately 25% Mizuna and 75% Day Neutral Strawberries for each fish tank growing area. Separate yield records will be maintained for each growing area after replanting until the removal of the fish at the end of the growing season. Based on projected demand, the decision was made to modify the planting ratio and all growing bins were planted with strawberries.

• Review of results indicates that several key nutrients may need further considerations. Based on challenges for  accurately modifying iron and calcium levels with organic materials, the decision was made to use mealworms only, without any supplements. No practical methods were available to modify the higher than desirable crude fats and fiber levels.
• Since the crude fat is higher than desirable for the mealworms, a preliminary study on a smaller sample of fish will be conducted to determine if the actual composition of the crude fat may be of concern for developing fatty livers. Not all forms of crude fats may be of concern. Further review with fish nutritionists will also be conducted.  Consulting with a fish vet may be needed to determine how to proceed for proper analysis of sampled fish. Fish necropsies for a sample population were conducted at the conclusion of the test project and results are discussed in the 2017 work activities below.
• Calcium and iron levels also appear to be significantly lower in mealworms and may need to be supplemented.
• Water sampling will be done to determine any need for supplementing minor nutrients through the biofiltration system for the mealworm fed fish tanks. Sampling will be done for both fish tanks and water source (pond water). Additional monthly sampling may be needed to maintain adequate minor nutrient levels.

• A preliminary smaller fish tank feed trial will be done with a small amount of bluegills and other fish species in early spring (prior to beginning feeding in the larger tanks) in the heated renewable energy greenhouse to determine if feeding with only mealworms could develop any problems. Early spring feeding tests showed no ill effects on a variety of fish, including Koi, Goldfish, Mosquito Fish, Yellow Perch and Bluegills.

• Feeding rates for the two larger passive greenhouse fish tanks will be determined based on dry weight nutrient analysis basis and the daily feed amount will be determined by minimum satiation rate of the fish, so that equal amounts will be fed to each tank throughout the growing season. It was determined that feeding live mealworms at twice the dry weight would deliver equivalent levels of crude protein.

• Fish from each tank will be harvested and weighed for sale in early October when the water temperatures are suitable for fish pond restocking. Due to a July fish kill, insufficient numbers of fish remained to justify resale for stocking ponds and the test was extended until mid-November. Ten fish from each tank will also be analyzed for any fatty livers or other internal differences resulting from the feeding regimes. This was done at the end of the test program in November.

• Plant tissue analyses will be sampled for both crops growing on top of both tanks in mid-summer as crops are actively growing. Due to lack of observable or measurable differences in physical appearances and yields of the strawberries, tissue was not sampled for analyses.

• Since my main assistant, Katie Aukerman, has moved on to a full time position in October at a different location, a new project assistant will be hired this spring. Other part time labor was also used to assist with the adult beetle separation process during the summer months.

WORK ACTIVITIES IN 2017

Mealworm production

• Research during 2016 determined that the optimum organic grain media was organic red wheat bran based on total numbers of mealworms; size of bran particles in relation to mealworms and texture allowed for effective sifting to remove mealworms and the price per pound of more readily available wheat bran. Spelt also rated closely to the wheat bran, but cost was a major consideration.
• Reused food bins that had previously contained fish were readily available from a local restaurant that produce was being sold to. Evaluations in 2016 determined that the deeper (5” deep) bins allowed for continued addition of wheat bran during extended growth of mealworms and the sides were high enough to discourage any climbing by adult beetles.
• Rectangular cutouts at both ends of the lids allowed for placement of mesh screening with a glue gun in a design that allowed for bins to be stacked at 90 degrees and not cover the screening.  This allowed for adequate air flow to prevent any mold growth in the bran. The mesh screened lids were not needed to keep mealworms from escaping, but were important for keeping any other insects out of the bins. 
• Plastic lids with shallow lips were placed on top of the bran in each bin to allow for placement of vegetable and fruit pieces as a source of moisture for the mealworms without having direct contact with the bran.
• During winter months from around November thru mid-June, organic potatoes were purchased and slices were used for providing moisture for mealworms. During summer months, cucumbers were preferred over potatoes, with apples and pears available for use during the fall months.  Best growth was realized during summer months with cucumbers being preferred over other vegetables such as carrots, summer and winter squash.
• Optimum sized slices appeared to be about ¼ to ½ inch thick. Thinner slices dried too quickly, thicker ones were more difficult for mealworms to extract moisture.  Slices were added on a weekly basis with any unused slices being changed out for compost to minimize any mold growth.  Mold growth was more of an issue with apples and pears, as these were grown without any pesticide applications and had a higher sugar content.  Less frequent addition of potatoes were needed during colder winter months.
• Based on literature research, there was a concern that adult beetles would cannibalize younger mealworms when density of the adults was high. In order to minimize this concern, adult beetles were removed approximately twice weekly and placed into a separate bin.
• This process of moving adult beetles was discontinued at the end of July.  Not only was it very time consuming to move the adults, but the desired results were not realized. Removing adults did not allow for any egg laying and subsequent replenishing of new mealworms in the original bins.  Similarly, the overcrowding of adult beetles in the separation bin did not allow for significant numbers of hatched mealworms to mature.  A second bin was used to reduce the adult beetle population.  Feeding adults from extra grain bins along with mealworm larvae to other fish tanks did not show any adverse effects and including adults in the sifting processes would be more time efficient.
• Subsequently, leaving adults in their original bins did not reduce, but rather increased replenishment.  Overcrowding of adults was not realized in these bins, but if this had become an issue, then it would be reasonable to remove some of the adults at that point.
• Measurements showed 300 mealworms averaged .050 lbs or 0.8 oz. This varied with stage of growth and related size of the mealworms, therefore feeding of fish was based on weight, not mealworm count.
• The initial amount of mealworms grown during 2016 and going into the 2017 ended up not being sufficient from the initial order of 5,000 mealworms in spring of 2016 to feed throughout the 2017 fish growing season. Additional orders of 10,000 mealworms were placed on April 25^th; 10,000 mealworms on June 5^th; and 30,000 on July 3rd.  These were distributed as evenly as possible to all existing mealworm bins (except for feed efficiency test bin) so as to minimize any disruption of mealworms available to feed fish.
• One bin was dedicated to measure the feed conversion rate, using 1.000 lb of wheat bran and 306 mealworms weighing 0.100 lb or 1.6 oz. No additional bran was added over the growing period, only vegetable and fruit slices were added to supply moisture.  The mealworms appeared to go through about 2 cycles from larvae to adults to larvae.  Final weight of the mealworms in this bin was 7.5 oz with 8.6 oz of frass.  Subtracting the initial 1.6 oz of mealworms, leaves 5.9 oz in weight gain over the growing period. 
• This represents a 3.2 to1 feed conversion ratio. This may be not as efficient as ratios seen in other research literature, suggesting there is an opportunity to improve on production practices or that the source of the grain may not be as efficient as other potential sources.  The stage of measuring weight gains during the life cycle may also have been a factor.
• Research literature suggests a 1.7 to 1 feed conversion ratio for live weight production from grain for crickets.
• Since the moisture content of the mealworms was determined to be 59%, therefore the actual weight of the dried mealworms would only be 2.4 oz. With a 21% analysis for crude protein, this means that only 0.5 oz of additional crude protein was produced from the 16 oz of wheat bran. The conversion rate in this limited test was closer to 32:1 with 32 lbs of grain resulting in 1 lb of protein. 
• This suggests that further research is needed to examine the feed conversion ratios to determine the economics when comparing to the use of grains as a protein source for fish feed versus use of mealworms.

Fish feeding

• Based on nutrient analysis of dried weight of mealworms as compared to Aquamaxx 400, it was determined that feeding fresh mealworms (60% moisture content) at twice the weight of the Aquamaxx would deliver the same amount of protein.
• It was determined from records of fish lost from the initial fingerling numbers of 375 placed in each tank in the fall of 2015, that there were 44 more fish surviving in LTE. Therefore 22 fish were moved to LTW, resulting in an estimated starting count of 300 fingerlings in each tank.
• Feeding began on April 10, 2017 when water temperatures were consistently above 52 degrees F.
• Feed rate was started at 0.10 lb of Aquamaxx in LTW and 0.20 lb of fresh mealworms to LTE.
• Based on observation when both feeds were consumed rapidly, the feeding rates were adjusted as needed during the summer months. The goal was to have all observable feed consumed within first 5 minutes after feeding.
• Feeding rate was increased on April 14^th to 0.20 lb of Aquamaxx and 0.40 lb of mealworms.
• Feeding rate was increased on May 1^st to 0.30 lb Aquamaxx and 0.60 lb of mealworms
• Scale that was weighing in lbs to the nearest .01 lb stopped functioning and was replaced with a new scale that weighed to nearest 0.1 oz on May 21^st. Feeding rate was kept approximately the same on May 21^st to 0.5 oz Aquamaxx and 1.0 oz of mealworms
• Feeding rate was increased on June 13^th to 0.6 oz Aquamaxx and 1.2 oz of mealworms
• Due to low amount of mealworms, had to use ones frozen the previous September of 2016 for five days, beginning July 5^th, while waiting on smaller mealworms to grow to suitable feeding size. Resumed feeding fresh mealworms on July 9^th.
• On July 17^th, a significant loss of fish was experienced. This appeared to be after a heavy rainfall turning pond water turned anaerobic. This foul smelling water was used to top off fish tanks on a hot day, resulting in sudden fish kill possibly from formation of ammonia or hydrogen sulfide gas. (See attached for more details relating to Fish Kill Event)  July-17-2017-fish-kill-summary
• After this fish die-off, feeding rates were adjusted based on new estimated numbers of surviving fish. Estimated 205 surviving in LTW and 110 in LTE.  Feeding began again on July 24^th and rates were adjusted to 0.2 oz Aquamaxx and 0.2 oz mealworms.
• Feeding rate was increased on August 5^th to 0.5 oz of Aquamaxx and 0.5 oz of mealworms.
• Feeding rate was increased on August 17^th to 0.7 oz of Aquamaxx and 0.7 oz of mealworms.
• Feeding rate was increased on September 4^th to 0.8 oz of Aquamaxx and 0.8 oz of mealworms.
• Feeding rate was increased on September 14^th to 1.0 oz of Aquamaxx and 1.0 oz of mealworms.
• Feeding was discontinued on October 30^th due to colder water temperatures of 50 degrees
• Fish were harvested, measured and necropsied at a Fish Health Workshop, (10 from each tank) on November 11^th
• The remaining fish were harvested and measured on November 13^th.

Harvesting mealworms for feeding fish

• Mealworms were generally harvested using a mesh screen colander with 1/16 inch sized holes that allowed for wheat bran to be sifted and fall through while mealworms were captured above the screen.
• At times there were sufficient numbers of mealworms at harvestable size that they were able to be handpicked from the wheat bran in the growing bins without sifting. This method was more time efficient, as adults would also need to be separated out during the screening process and put back into the growing bin.
• Mealworms were purchased as assorted sizes which allowed for various stages of growth. It appeared to take about 3 weeks to grow from smallest sizes to adult beetles, depending on temperatures. At low temperatures below 55 degrees, growth appeared to slow and at temperatures about 85 degrees growth may have also been slowed possibly due to lack of moisture available from cut up pieces of vegetables from rapid drying.
• The hand harvesting generally took about 5-10 minutes per oz of mealworms, depending on density of suitably sized mealworms in each bin. Mealworms were hand harvested when there were sufficient numbers of these mealworms in the bin to easily pick off the surface, otherwise screen sifting was the preferred technique.
• Sifting harvests were more variable and took anywhere from 5-25 minutes, again depending on density of suitably sized mealworms in each bin and numbers of adults to hand pick off the screen to be returned to the bin.
• By midsummer, especially when wheat bran had been thoroughly converted to frass in many of the bins, the sifting process also became very dusty and required a dust mask. Anyone with allergies, especially to wheat based products, might suffer from inhalation of the fine dust particles.  Further refinement of this process is needed to figure out how to minimize dust.  The bins were never dumped out during the growing process due to eggs being present in the frass and the desire not to lose them. 
• Fresh wheat bran was replaced regularly, as needed, to provide a readily available source of feed for mealworms.
• Daily sorting and weighing of mealworms was a time consuming process. To be more efficient it is recommended to use larger growing containers to grow more worms for a mass harvest and then possibly freezing, refrigerating or drying them to be able to more easily scoop with a premeasured container.

Feed to protein conversion efficiency

• One bin was started on March 27^th with 1.000 lb (16 oz) of wheat bran and 0.100 lb (1.6 oz) of mealworms (306 mealworms).  These mealworms were about double the size of those received in 2016.
• Only vegetable and fruit slices were added on approximately a weekly basis to provide needed moisture for mealworm growth. No additional wheat bran substrate was added.  After about 2-3 months there was virtually no remaining visible wheat bran, just mostly frass.  Adults beetles were allowed to lay eggs and hatch out. Larvae continued to grow and mature, apparently continuing to feed on the frass.
• Final results were recorded on November 1st, with all larvae counted and weighed.
• Final count was 3,154 mealworms weighing 7.5 oz with 8.6 oz of frass.
• This represents about a 10 fold increase in the numbers of mealworms with a 4.7 fold increase in the weight of the mealworms.
• The total final weight of mealworms plus frass was 16.1 oz, as compared to starting combined weight of 17.6 oz. This is an unexplained loss of 1.5 oz.  Possibly due to evaporation from dead larvae during the multigenerational period of growth.
• If the initial 1.6 oz of mealworms is removed from the equation, then only 5.9 oz of new mealworms were created from the 16 oz of wheat bran.  This results in a conversion rate to 2.7 to 1. 
• The actual dry weight of the protein in the wheat bran was not determined. Since the fresh weight of the mealworms is about 59% moisture, then the actual crude protein content was 21% based on dry weight.  The dry weight of the mealworms was 41%. If an adjustment is made for the moisture content, then the conversion of 1 lb of wheat bran to crude protein resulted in an additional 0.5 oz of protein. 
• The 1 lb of wheat bran resulted in 5.9 oz of new mealworms or the equivalent of roughly 3 oz of commercial feed protein.
• The price of the wheat bran was about $1 per pound and was similar to the cost of the Aquamaxx at $1 per pound. One pound of Aquamaxx has 7.8 oz of crude protein and is valued at 49 cents.  One pound of wheat bran grows only 0.5 oz of crude protein.  To grow an equivalent amount of crude protein from mealworms in theory would require 15.6 pounds of wheat bran.  Therefore preliminary indications are that the cost of crude protein, based on this limited test would be significantly higher than commercial feed and may not be economically justified.
• Furthermore, the added cost for a vegetable or fruit source for moisture was not factored in to these calculations.
• Just to clarify, this was a limited, non-replicated test. The various stages and sizes of the harvested mealworms may have been a factor and harvesting at the maximum larvae stage could have resulted in more favorable results. Using just one bin over a 7 month period may not have been an accurate reflection of potential conversion rates.  A more replicated study should be done to better determine a more accurate conversion efficiency ratio.
• There is a definite need to improve the conversion of wheat bran or other grains to actual harvestable live feed by either more efficient production methods to maximize harvesting at the right stage of growth or modification of growing substrate to include a better balanced blend of nutrients, possibly from multiple sources of grains.

Strawberry Yields

• Strawberries were harvested from April 20, 2017 through November 6, 2017 twice weekly. Only usable berries were counted and weighed at each harvest.  Those with any rotten spots or smaller than ½ inch in diameter were discarded.
• Virtually no differences were observed between strawberries harvested from different tanks. The LTW had a total of 3,937 berries weighing 1,245.9 oz for an average weight of 0.32 oz. The LTE had a total of 4,004 berries weighing 1,264.3 oz for an average weight of 0.32 oz.  The slightly lower numbers of harvestable berries from LTW were most likely the result of insect or disease pressure, not nutrients absorbed through capillary rope wick watering from the fish tanks. (See attached Strawberry Yield Data) Strawberry-yields-SARE-project-2017

Fish Yields

• Estimated numbers of fish in each tank did not match with the actual numbers at the end of the test period. After the July 17^th fish kill, it was estimated that the remaining numbers were 205 in LTW and 110 in LTE.  The actual numbers were 129 in LTW and 43 in LTE.
• This was likely due to the fact that not all the dead fish floated to the surface for removal from the July 17^th event, thus not being counted. It is also possible that a similar miscalculation of the numbers in each tank may have occurred at the beginning of the testing period.
• This means that the actual feeding rate per fish was 1/3 higher for the fish in LTE fed mealworms, as compared to the fish in LTW fed Aquamaxx after July 24^th. This needs to be considered as possibly skewing the total yield numbers.
• Ten fish were harvested on November 11^th for necropsy and the results are discussed in the next section.
• The average length of all the Aquamaxx fed fish was 145.6 as compared to 133.1 for the mealworm fed fish. The average weight of the Aquamaxx fed fish was 48.7 as compared to 47.1.  It is difficult to determine any statistical significant as the treatments were not replicated, but it appears that the Aquamaxx fed fish were on average about 9.4% longer and  3.4% heavier. (See attached Fish Yield Data) Fish-yields-SARE-project-111317 (Special thanks to Dr. Bill Lynch for his assistance with measuring and weighing all the fish on a very cold day!)
• There were no visible differences between those fish fed exclusively mealworms as opposed to those fed commercial feed, however, subsequent necropsy revealed concerns with fatty livers being greater for those fed mealworms.

Necropsy Results

• Ten fish from each tank were harvested for necropsies on November 11^th. Fish were randomly selected but any under 30 mm in length were returned due to being too small to dissect without potentially damaging internal parts.
• These fish selected for necropsy were included as part of a larger training program with additional fish also being studied. The event was offered as part of a Fish Health Workshop by the Ohio Aquaculture Association at the Ohio Department of Agriculture in Reynoldsburg, Ohio. Students and attendees dissected the fish, while the fatty livers were evaluated by Dr. Stephen Reichley, Director of Fish Health at Clear Springs Foods in Buhl, Idaho
• One of the fish from the mealworm batch was not evaluated due to the loss of the label during the evaluation process.
• Fish were evaluated by Dr. Reichley with descriptions of the extent of liver damage. A scale of 1 thru 5 was developed to rate his descriptive evaluations with 5 being a good liver and 1 being a totally nonfunctional liver, being white indicating a total fatty liver. 
• The fish from the mealworm batch showed significantly more liver damage with an overall rating of 2.1 as compared to Aquamaxx fish with an overall rating of 3.9.
• None of those with the Aquamaxx were totally encompassed fatty livers, however 3 had ratings of 3 or below with 4 of the 10 livers being in good condition. On the other hand, 4 had totally encompassed fatty livers with 8 out of the 9 livers from the mealworm fed fish having ratings of 3 or below, with only 1 having a good liver.
• Fatty livers are usually the result of improper feeding or imbalances in the feed. The reason it was decided to do necropsies for liver problems was due to the significantly higher crude fat content of the analyzed mealworms as compared to the commercial feed.
• The fact that even some of the commercially fed fish had less than ideal livers indicates that fish may have been overfed or that the commercial fish feed made not have been correctly balanced for this stage of growth of the fish. Based on the final fish counts being less than expected, overfeeding of both tanks might have been a consideration.  In the case of the mealworm fed fish, this may have been even more of a factor, as these were fed 1/3 more per fish than what was fed to the commercially fed fish due to inaccurate estimation of the numbers of fish in the tank after the fish kill event.

Water Quality

• The in-ground fish tanks each measured 4 ft x 3 ft x 16 ft and when filled to about 2 inches from the top held approximately 1300 gallons of water.
• They were initially constructed and filled in 2015 using pond water. Subsequently, they were periodically topped off as needed, to replace water due to evaporation using the pond water.
• Initially several goldfish were placed in each tank to evaluate water quality as being suitable for fish prior to stocking with bluegills.
• In October of 2015, 375 hybrid bluegill fingerlings measuring 2-4 inches were added to each tank.
• The two tanks were designated Long Tank East (LTE) and Long Tank West (LTW) based on their location in the Passive Solar Greenhouse (PSG).
• Fish were fed with Aquamaxx 400, a commercial feed, during 2016. When water temperatures dropped below 52 degrees F in the late fall, feeding was discontinued.
• Initial water quality testing began in March of 2017, with additional testing in June, July and November. (See attachment for Water Quality Analyses 2017) Water-Quality-Analyses-2017
• Key parameters showing differences or that were out of optimum range:

March

*(Previous well water testing done in 2003 showed 54 ppm Sodium)

June

July  (4 days after fish kill event)

November

• Less than ideal parameters especially for nitrates, hardness, sodium and sulfates may have negatively impacted the growth rates for all the bluegills in this test program.
• Although the primary source of water for filling the pond was from rainfall, during drought periods, well water was used to keep the water level sufficient for irrigation. This likely resulted in accumulation of the higher than desirable levels of hardness, sodium and sulfates in the pond water.
• Significant differences were not observed for water quality parameters based on the different source of feed in the two fish tanks.
• The general trend was for slightly higher nitrate levels in the LTW tank. The starting level was even higher and this might have been the result of accumulated excess feed from the previous year.  Both tanks had been fed identical commercial feed amounts during 2016, but when calculations were made to adjust fish counts based on losses over the previous year, there were actually fewer fish in LTW. 
• This slightly higher level of nitrates in LTW was also observed throughout 2017. This may have been the result of less digestibility of the commercial feed as compared to mealworms and further accumulation of residue.
• The estimated fish kill numbers from the July 24^th event suggested that the ratio of remaining fish in LTW compared to LTE was 2 to 1. Feed rate was adjusted accordingly. The actual numbers at the end of the test period were actually 129 in LTW and 43 in LTE.  This was a 3 to 1 ratio. Therefore the adjusted feeding rate per fish was actually higher for the LTE. The amount of fecal material may have been higher due to more fish in LTW, thereby keeping the nitrate levels slightly elevated. 
• Even though feeding higher rates, the LTE tank fed mealworms continued to have lower nitrate levels. This might suggest that mealworms may be slightly favorable for keeping nitrate levels at more reasonable parameters.

Temperature Parameters

• Data logging temperature sensors had been used for previous research projects and additional sensors were purchased for recording temperatures in various locations for this project.
• These sensors included outside temperature, air temperature in the Passive Solar Greenhouse (PSG), soil temperature in the PSG, water temperature in both the Long Tank East (LTE) and Long Tank West (LTW), root zone temperature in the strawberry bins growing above both of these tanks, and inside a Mealworm bin located inside the main greenhouse in a back room not exposed to any direct sun.
• A more detailed summary of the ranges of temperatures for these sensors was compiled. (See attached file Temperature Data Summary) Temperature-data-summary-SARE-Project
• The following table represents a summary of data over about a 16 month period of time dating from July of 2016 thru the middle of October of 2017, when most all of the sensors were functioning properly. Some issues with moisture and battery life did not allow for consistency over the last months of data collection and were limited during the winter of 2017 – 2018.

Range of temperatures from July, 2016 thru mid October, 2017 in degrees F.

• Air temperatures inside the PSG generally ran about 10 – 15 degrees warmer than outside temperatures.
• Soil temperatures measured at 3 inches below ground inside the PSG did not freeze during the winter months that saw outside air temperatures as low as 0 degrees and inside air temperatures as low as 10 degrees in the unheated greenhouse.
• Similarly, the in-ground fish tanks did not freeze during winter months and were generally 10 degrees warmer during the winter and 5-10 degrees cooler during the summer than the soil temperatures.
• A slightly higher maximum temperature was recorded for the LTE as compared to the LTW and this may have been an anomaly, rather than a measurable, consistent difference in the fish tanks.
• The root zone temperatures for both tanks were virtually identical and they were similar to the soil temperatures, but warmer during the summer months due to greater sun and air exposure above the fish tanks.
• The root zones also did not experience any freezing temperatures as these had a frame above the strawberries to support polyspun bonded row cover material that was placed over the support frame during nights when outside temperatures below freezing were expected. The water temperatures were kept from freezing due to geothermal transfer in below ground portions of the fish tanks and this provided heat to prevent freezing of plant root zones.
• Slower growth and lack of pollinators was observed during the colder winter months of December thru February, thereby reducing any saleable strawberries until about the middle of April. This corresponded closely with water temperatures below 52 degrees in the fish tanks, which was the critical temperature to begin or stop feeding of fish in the tanks.
• The mealworm bins were located in the main greenhouse which also had some supplemental heating to keep the main greenhouse temperatures about 45 degrees F during the winter months and therefore did not experience any freezing, although due to their distance away from the main heating source, the temperature did drop as low as 37 degrees F and some loss of adult beetles was observed.
• The mealworms were generally odor free, however, as temperatures warmed the smell of the rotting adult beetles was noticeable.
• The low temperature did not appear to cause any loss of mealworms, however, activity and feeding generally didn't occur until temperatures rose above 50 degrees with the optimal feeding range being observed from 60 – 85 degrees.
• Providing adequate moisture with vegetable or fruit pieces during hotter weather for the mealworms was seen as critical to maintaining active feeding and growth as these pieces tended to dry out more quickly at temperatures above 80 degrees.

Labor

• A part-time assistant, Sonora Furber, was hired in the spring of 2017 to assist with the project. Considerable more hours than expected were spent initially with separating adults on a weekly basis.  This was discontinued during the summer due to observations that separating the adults did not allow for enough egg laying in the bin prior to their removal to hatch out enough new mealworms.
• Harvesting and feeding mealworms and commercial feed to the fish was done by the project coordinator.  As mealworm populations decreased in each bin the time spent harvesting increased.  This also involved more hours than expected as this task was done on a daily basis from mid April through the end of October.
• Harvesting, counting and weighing strawberries was done by the project coordinator and part-time assistant and also took more time than expected due to the need to harvest twice weekly.