A Soggy Intro
Heart 2 Heart Farms where I have been working has an aquaponics greenhouse that was built, but never fully brought online as the person who was working on the project left.
Aquaponic system design and operation is something that I have had an academic interest in and getting this greenhouse up and running is the perfect opportunity to get my hands dirty - or wet - as the case may be.
In this series I will be documenting the process of refurbishing the system, adding some tech integration, seeing what kind of food we can pull out of it, and generally keeping track of my learnings.
In the first post I want to write an overview of the system, what it’s being used for currently, the issues that need to be resolved, and an overview of some future improvements.
System Overview:
The greenhouse contains two independent and identical aquaponics systems which consists of the following:
A 2500 Gallon above ground pool that acts as the main fish tank. This is connected to a barrel with a bottom feeding siphon and an overflow pipe in the side of the pool wall.
A 55 gallon barrel that was going to be the solids filter, but was not finished. The barrel has outflow pipes about halfway up going out to the grow beds.
Plastic grow beds with a clay aggregate grow medium.
A heavy plastic lined grow pond which looks to be 20’ x 6’ x 2’ or about 1700 gallons.
A 275 gallon IBC - intermediate bulk container - acting as a sump tank.
A submersible pump - I will work to determine the type and flow rate in the future.
A Diagram of the system with water flow direction:
Some pictures of the system:
Current Useage
Both pools contain a large population of mosquito fish - a small fish that as the name implies eats mosquito larvae. These fish have been introduced to every body of standing water on the farm in order to cut down on the mosquito population. The fact that these fish can thrive is a system that is not well maintained and without any type of feed input makes them a fantastic choice for the purpose of nutrient generation.
The Grow beds themselves are not currently being utilized for any plant production. However I would assume the surface area of the clay aggregate is acting as a biofilter - essentially a bacterial colony that converts ammonium from the fish into nitrates that can be taken up by plants.
The grow ponds were at one point used to grow ornamental water plants. Some of these water plants that have continued to thrive in the environment and provide habitat for both the fish and some frogs that live in the ponds. Seeing the frogs was a great sign of overall ecosystem health as their delicate skin is very sensitive to toxic contamination.
The south pond is currently being used to grow duckweed. Duckweed is an informal name of the Lemnoideae subfamily of plants. These are the smallest flowering plants, some of the fastest growing, and incredibly nutritious. Duckweed has an an average protein content of 25% by dry weight. As a comparison cooked lean beef has about 27% protein by weight. Not too bad for some pond scum! It is able to outcompete algae by blocking light below the surface so the south pond is nearly algae free while the north is overgrown with it. The duckweed is also currently being used to supplement the livestock feed on the farm.
In the future I would love to experiment with using it as a food source for human consumption. Although for now it seems most people are interested in using it for a livestock feed supplement.
Current Issues
As alluded to in the previous sections there are a few issues with the current aquaponics system:
The rate of water flowing into the pool from the sump pump is much higher than the rate at which the siphon and overflow pipe can take water out of the pool. Because of this imbalance the pump has not been able to run for more than 15-30 min before the pool starts to overflow. This leads to a buildup of waste in the pool, low nutrient flow out of the pool, and poor aeration. This is the biggest issue to overcome before any other work is to be done on the system.
The overall design of the barrel does not act as a efficient solids filter.
The grow beds are not draining properly.
Proposed Solutions
https://aquaponicgardening.ning.com/profiles/blogs/how-we-build-our-solids-lifting-outlet-slo-at-smoky-mountain
In order to increase the outflow of the water from the pool a larger diameter siphon will be used. Ultimately I will try a solids lifting outlet (SLO) in order to increase both the outflow of water as well as how much waste is being removed from the tank. An SLO will provide a way of lifting up solids from the bottom, prevent a siphon from emptying the pool in case of a power failure, and not require a siphon prime when restarting the system.
Or so the claim is - I have not personally used the system but am looking forward to testing it out.
For the solids filter I will be testing out a radial flow filter. This simple design settles solids at the bottom of the filter while outputting the nutrient rich water out of the top.
Finally I will add bell siphon to the existing beds in order to improve how the water is drained out of the medium.
Radial Flow Filter:
https://www.youtube.com/watch?v=sBCC9tMsleY
Bell Siphon:
https://www.youtube.com/watch?v=Ia1BQFTaG7c
Thanks for reading this first post! I will update this blog with further progress as it happens.