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Aquaponics: Our Status and Goals

Aquaponics: Our Status and Goals by Lindsey Grolmes

 

Aquaponics is the process of growing crops hydroponically in combination with aquaculture. Aquaponics is a great way of creating a sustainable food production system that can in part care for itself. In aquaponics systems, the waste that the fish produces filters through plant roots which fertilizes the plants and the plants filter the water to be added again to the water for the fish. This system is mutually beneficial for both fish and plants and mimics the process that occurs naturally in lakes, streams, rivers, and other bodies of water. Plants in aquaponics also have availability to the nutrients in the water all day long, meaning that faster growth rates can occur in comparison to growing in soil.

At The Jewel of Encanto Farm, we have several aquaponics systems that house Tilapia. Our outdoor aquaponics systems include a pond and several levels of shelves for growing food. The upper shelves contain lava rocks as a growth medium and are where we grow lettuce and herbs. The lower shelves are used to grow duckweed, which is a small self-propagating aquatic plant that we feed to our ducks and chickens as an essential source of protein. The trays with duckweed do not need a growth medium and the tiny plants simply float on the surface of the water.

Currently, our entire tilapia stock is contained within these two ponds while our indoor area is undergoing renovations. Once the indoor area is done, we will re-setup three other tanks with aquaponics shelves for growing greens, herbs, and duckweed for our animals. The previous system we had indoors used lava rocks on all the shelves as a growing medium, and while lava rocks can be a good medium for aquaponics growing, we are going to be trying a new medium this time around. From our experience, the lava rocks were difficult to clean, attracted insects, and were not easy to move out of the system. Because of the rough surface of the lava rocks, it is easier for grime to get stuck to the surface and build up over time. We also found that when planting root intensive crops like water spinach in our lava rock bins, the roots in combination with the heavy lava rocks started to put too much pressure on the plastic bin. Having a lighter weight grow material would lessen the pressure on the aquaponics containers. This being said, our negative experience with lava rocks has mostly pertained to our indoor systems, our outdoor aquaponics still have lava rocks as the growth medium and all aspects of the system are working well. The issue we had with lava rocks could reflect the fact that in the indoor setting there is less airflow and lower water pressure, which reduced the system’s ability to keep grime and insects off the medium.

In order to create a cleaner surface when we redo the system, we will try a Styrofoam floating raft sheet. These foam sheets will be cut to size and then growing plugs will be made for the rooted transplants to be added to. While the foam sheets do not last as long as lava rocks, they will be easy to maintain, clean, and cheaper to replace. Because the Styrofoam floats on the surface of the water, the water passing through the roots will be cleaner and flow more easily through the system.

We hope that this system will prove to be cleaner and easier to maintain over the long term; we also hope to add fresh water prawns to one of our tanks to add a different type of fish stock. We will continue to post updates on our aquaponics journey and what we think works best for us!

 

A Few Aquaponics Tips:

 

-Check your Ammonia and Nitrate levels in the water regularly to avoid killing fish stock. This can be done with a simple test kit at home. If your levels are too high, you will need to drain and replace the water until the levels are suitable again.

-Air circulation is essential. If you are growing outdoors in an open space then you are all set; if you are growing indoors, add fans to your grow space to help air flow.

-Whether you use lava rocks, clay balls, or a floating system, make sure your growth medium is clean and free from buildup of grime.

-Try a variety of plants in your aquaponics system to see what works best for you. So far at the farm, we have had the best luck with varieties of lettuce, romaine, basil, mint, water spinach, cilantro and parsley.

-If you have an outdoor system, you will need to heat your pond to ensure the fish can live during the colder months.

 

     

Duckweed growing in an aquaponics shelf.              Lettuce growing in Lava Rocks.

 

 

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