Increasing Farm Income and Diversification By Converting Abandoned Manure Pits Into Aquaculture Production Facilities

Final report for FNC17-1105

Project Type: Farmer/Rancher
Funds awarded in 2017: $20,406.00
Projected End Date: 12/31/2019
Grant Recipient: Blue Iris Fish Farm
Region: North Central
State: Wisconsin
Project Coordinator:
William West
Blue Iris Fish Farm
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Project Information

Description of operation:

Bill West runs Blue Iris Fish Farm, a 40 acre facility containing nine culture ponds and 12 culture pond-side tanks. Blue Iris is located approximately 12 miles north of Appleton, WI. Blue Iris specializes in the culture of perch and bluegill mostly for the fish food market. Blue Iris conducts research to enhance culture production and grow-out. A SARE grant (FNC08-731) and Wisconsin ADD grants 21014 and 24023 completed work on elimination of digenetic tremetode infestations of perch and bluegill and completed an in-depth assessment of creating a fish cooperative. Blue Iris participated in a federal feed study (least cost diet studies conducted by North Central Regional Aquaculture Center (NCRAC) in 2012). Blue Iris also participated in a study with Milwaukee School of Freshwater Sciences in comparing grow-out of perch using a fish vs non-fish meal diet. Blue Iris currently works with local high schools in providing fish, feeds, and research ideas for local agriculture programs (current SARE Grant FNC16-1064 described as an attachment).

Dick and Tami Hallam have been farming for 23 years. Their 47 acre farm was downsized in 2011 to a 7.2 acre hobby farm and they still retain all the farm buildings and the manure pit. The manure pit was abandoned about 1989, i.e. drained for safety concerns with raising a family. The Hallams have constructed an indoor aquaponics system. This grant will allow them to refill the manure pit and focus on raising their own feed trained perch fingerlings for their use and sale.

Dan Knutzen has taken over the family farm in 1988 and has converted the dairy to mostly grains and hay. He currently works his 200 acres and rents an additional 100. The manure pit associated with the dairy has been non-operational since 2000 but still contains about 2 million gallons of water for aquaculture use.

Vic Vosters owns a 60 acre farm that has been in the family since 1946. The farm originally was dairy then beef, and now grain. The manure pit which once served the dairy operation holds about 1.8 million gallons and is now unused. The pit has been out of use for about three years so this site could potentially need the most scrutiny from the standpoint of water quality. Vic would like to see if he could create a significant source of income from the use of the now vacant manure pit. This study would provide him water quality assessments which would provide information relative to pursuing aquaculture at his farm.


Small dairy operations are slowly being converted to larger operations, beef cattle or grain operations leaving behind hundreds of manure pits which are ideally designed and suited for use in the aquaculture industry.  This project will evaluate the water quality of abandoned manure pits (abandoned from between 3 and 18 years) to determine suitability for raising fish.  Water quality sampling will be conducted over a two year period in all four seasons and include both horizontal and vertical sampling locations in each of three pits. If water quality is determined to be suitable for fish, an evaluation of suitability for fry, fingerlings and broodstock will be conducted as will the grow-out of fish using pond-side tanks.  Results of these efforts will be shared with the local farming community as well as local extension personnel and land-use coordinators.  

Project Objectives:

As dairy operations consolidate in the United States, many small farms are converting over to alternative livestock and/or grain operations. This leaves hundreds of engineered manure pits vacant – over two dozen in Outagamie County, WI alone.  Most of these pits have been designed to meet standards to prevent leakage i.e., concrete, synthetic lined or clay lined.  Once the pit is no longer used, it is normally required to be abandoned and there are regulations for proper abandonment which mostly deals with the liquid and solid waste in the pit.  Regulations also allow the pit to be reused including for such uses as aquaculture.  In order for the pit to be used for aquaculture, the water contained within has to be deemed suitable for raising fish.  The Outagamie County Land Conservation Coordinator has indicated that these pits do not have to be abandoned if used for aquaculture as this will be considered continued farm use.


At the same time that these pits are becoming available, the aquaculture industry is seeing a significant demand for food fish. Live catch of perch from the Great Lakes has been significantly lower in the past three years and the industry cannot ramp up production fast enough.  The actual cost for Great Lakes perch fillets has gone from less than $10 per pound in 2013 to over $13 per pound in 2014 and predicted much higher for Lent in 2017.  There is a genuine lack of water resources [ponds or indoor Recirculating Aquaculture Systems (RAS)], the ability to permit more outdoor systems (expansive pond culture systems), and there is virtually no one providing feed trained fingerlings for use in indoor (RAS) or aquaponics systems.  The aquaculture industry absolutely has to rely on alternatives such as vacant manure pits to solve some of these capacity problems. 

This project will focus on three objectives. One, there will be a need to conduct water quality assessments on existing manure pits to determine that chemical parameters present are compatible with fish culture.  These assessments will be conducted multiple times in each pond for two years to determine affects of temperature seasonally and will also be conducted as a vertical profile.  Here we will need to determine if any of the ponds stratify and isolate water quality top to bottom.  We believe that since the ponds have aged significantly since last used, most organic matter will have settled and has digested (converted to inorganic solids, gases or liquid over time).  Therefore the oxygen demand should be much less. This project will use three pond settings, one recently abandoned (three years at initiation of study), one that has been unused for 15 years, and one that was drained and will be refilled for the project.

The second objective is to conduct fish studies. Here we will use perch in several alternative situations.  Depending on the immediate water quality, perch may be introduced as eggs, fry, or fingerlings.   For this project we will either transfer gravid eggs to observe hatch and fry production, stock with fingerlings to obtain feed trained fingerlings for commercial use, or install pond-side grow-out tanks for demonstration of grow-out from four to eight inches in size in one summer.

Finally, we hope to provide former dairy farmers with a good use for the unused manure pit. With the use of the pit as a resource for aquaculture, the farmer will be able to diversify his crop and provide an alternative source of income.


Click linked name(s) to expand/collapse or show everyone's info
  • Dick and Tami Hallams
  • Dan Knutzen
  • Vic Vosters


Materials and methods:

For the first year of this project, we had to spend a significant amount of time gathering data.  We have the ability to supply fish to manure pits as eggs, fry, fingerlings or adults and we also have the option of putting in pond-side growing tanks which use water from the pit but the fish are in the tank not the pond.  We had manure pits that had not been used for three years (#1), fifteen years (#2), and one that had been pumped out (cleaned) but empty (#3).  The first two ponds could be immediately assessed for water quality however, the third pit needed repair to hold water again. 

Pond-side tank with dock, intake, and pump.

Because there was no data regarding water quality, it was decided to release no fish directly into any pond the first year.  We did not attempt to raise fish in tanks at Pit 1 because it was felt that water quality was not sufficient .   We did successfully raise fish in a pond-side tank using water from Pit #2 through July.  Then, as in Pit #1, we ran into a situation where we could not overcome the ammonia generated at the level of the intake structure for the pond-side tank. 

Research results and discussion:

Both pits #1 and #2 had fairly good water quality May into June 2017.  However by mid June pit #1 was already seeing significant algae growth.  Pit #2 also had algae growth, less than Pit #1 but also had a surface coating of duckweed.  What we found was that as we conducted the vertical water profile there was adequate oxygen at the surface because of the algae but because there was so much algae sunlight penetration only reached the top foot or two.  Eventually we lost all oxygen except for the first foot and lower depths saw an increase in ammonia.  We could probably keep fish alive in a tank by pumping only oxygenated surface water but we risk too high of temperatures during the day, and severe oxygen depletion at night.  So it appears that while Pit #2 was rested for 15 years, it still retained a significant nutrient loading which is not used up within the pond dynamics. Soluble nutrients will continue to circulate in the pond until removed.  We are continuing to conduct water quality assessments throughout the fall, winter and spring to document the water quality. 

Pit #1 operation dropped out of the program at the end of 2017.  Pit #2 was continued to be monitored through 2018 to verify results and observations from 2017.  Just at spring breakup in 2018 mid-eastern Wisconsin had a late blizzard burying open water with 24+ inches of snow.  It is unclear if this had a significant impact on pit water dynamics but instead of having higher water quality in the pit going into summer, the ammonia spiked and there was a total loss of duckweed the entire summer.  So, it appears that these ponds are not stable nor predictable with respect to water quality.  For 2018, Pit #2 never did recover water quality and is not a candidate for perch culture without intervention.

In addition to the observations, vertical water profiles were conducted for several analytes including hardness, alkalinity, ammonia, pH, nitrite-nitrogen, nitrate-nitrogen, and oxygen.  In general, we found that Pit 1 and 2 both had very high hardness and alkalinity.  Ammonia did not figure to be a factor (with respect to toxicity) until July and into August in 2017 and this was true from about the two foot line down to the bottom.  Ammonia could be removed by aeration - which was not provided the first year. 

Pit #3 was repaired and began filling in 2017.  Preliminary water quality assessments suggested that we should be able to add fish directly to the pit as well as to a pond-side tank.  Installation of docking and tank occurred prior to the 2018 season.  It took all of 2017 and part of 2018 to find and patch leaks in the berm but by 2018 there was sufficient water to hatch and feed train a batch of fish.  Two different batches of fish were added to the pit.  These included several ribbons of eggs in April (possibly lost in the blizzard) and 1000+ feed trained fingerlings in June.  Seining in the fall indicated that the fish not only thrived but because they were feed trained, their average length was between 5 and 6 inches (better than 1 inch per month growth).  These fish will be cold banked over winter at the Hallam's then placed in the pond-side grow-out tanks next spring for a total egg to table window of 16 months including over winter. 

Since the beginning of the project, there has been a significant amount of interest in the project and the project's potential.  We have given a presentation to the extension personnel at Brown County.  This is important because it is the County extension services that have direct contact with all the farmers that would have manure pits which either are or could be abandoned.  In addition, we are also getting cold calls from other farmers in a third county and from Minnesota who have cleaned out pits and are ready to add aquaculture to their facility.


Participation Summary
5 Farmers participating in research

Educational & Outreach Activities

2 On-farm demonstrations
1 Online trainings
2 Tours
1 Webinars / talks / presentations

Participation Summary:

30 Farmers participated
3 Ag professionals participated
Education/outreach description:

We are working with the Outagamie County Extension service as the primary link to end users.  The extension service was able to provide us a list of farmers who might at least want to learn more about what the project entails.  From that list we developed an interest from three who wanted to participate.  Since that beginning, we also were in touch with Brown County Extension service and gave a presentation to about eight personnel.  Two of these came onsite to Blue Iris Fish Farm to see the operations.

During the summer of 2017, we held an open house/field day for the local community.  We advertised in a local newspaper that is circulated over a several county area.  We also advertised on the Wisconsin Aquaculture website which brought participants in from over 100 miles away. 

In June 2018, Blue Iris gave a presentation at the Mid-west Energy Fair in Custer, WI. relative to repurposing farm manure pits.  While this event attracts thousands over three days, the presentation was attended by about two dozen from several states.

Learning Outcomes

5 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Lessons Learned:

From the onset, this project was intended to assess the possibility of using abandoned manure pits for the purposes of aquaculture.  Since many of the manure pits are engineered facilities, there may be regulations as to the disposition of the wastes within the pit as well as the disposition of the pit itself.  What we find is that once a pit is no longer used, many times it is left (manure remaining) until it is required to be properly abandoned.  One option that is allowed in Wisconsin is to reuse the manure pit for other purposes such as aquaculture.

For this project we intended to assess the water quality of several abandoned pits to see if water quality could be sufficient over time (5, 10, 15 years) to raise fish without first removing the liquid waste.  The idea is that over time the organic solids would decompose and inorganics would become part of the substrate.  In addition, many of the ponds are deep, narrow, and possibly not affected by wind as a natural lake.  Therefore, perhaps settled inorganics and nutrients would settle and not become part of the water column during spring/fall turnover.

What we learned the first year is that recently abandoned manure pits have a significant nutrient load which equates to excessive algae growth all summer.  The pit that had been abandoned for 15 years still had a significant nutrient load.  This points out the fact that there was nothing removing the nutrients as they were just being recycled within the pond.  This was verified in 2018.  One would think that similar to a natural lake eventually higher aquatic plants would become established and compete for nutrients.  This is possible but based on what was observed, algae growth and Lemna outcompete higher aquatic plants for nutrients (substantial blooms in April) which effectively shade out higher plants. 

What to do with the excess nutrients?  This waste should probably be land applied according to protocols established for manure pit abandonment.  The one thing that has not been considered is to use the soluble nutrients in an aquaponics operation.  This might work if the waste was aerated to convert ammonia to nitrates and other essential micro and macro nutrients were sufficient or supplemented.

Another factor which was learned throughout the study was the derivation of solids in the manure pits.  Some manure pits are single cell while others are multiple cells.  Farmers use a number of media for bedding.  Therefore not only will a manure pit be filled with animal waste but also inert waste such as sand, sawdust, straw, etc.  Inert waste will not digest as does animal waste and will tend to fill a pit robbing it of capacity.  These materials have to removed from the pit in order to regain capacity sufficient to restore water quality dynamics conducive to raising fish.

To date, there is nothing from the project data that suggests that once cleaned, the former manure pit cannot be used for aquaculture.  We have one participant in the project that has proven that a manure pit can be productive. 

Project Outcomes

1 Farmers changed or adopted a practice
5 Grants received that built upon this project
3 New working collaborations

Information Products

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.