CREATING A CLOSED LOOP
During the 2017 fall semester, I completed an aquaponics studio in the RISD Nature Lab. Aquaponics is the practice of growing plants with water inhabited by fish. Waste produced by the fish is broken down by microorganisms and converted into fertilizer for the plants, which in turn filter the water as it returns to the tank. This codependent ecosystem uses 90% less water than it would take to grow the plants in soil and half the time. Throughout the semester, I worked with classmates Westen Johnson and Nick Burger to build and balance our aquaponic food production ecosystem.
Our system was built using a 130-gallon fish tank, PVC piping, two LED grow lights, two separate grow beds and variety of pumps and filters. The system was chosen by RISD administration as an exemplary project that illustrated why aquaponics is an important development in the future of food production. As a result, the system will be installed in RISD’s dining hall, The Met, as a reminder to students of their commitment to fresh, sustainable and nutritious food.
- Our system is capable of growing a variety of plants. During our trial period we chose to grow lettuces, watercress, and basil because they’ve been proven to grow well in aquaponic and hydroponic scenarios.
- Goldfish are some of the best fish to use in small scale aquaponics systems. They are low maintenance and produce a lot of waste. We had five goldfish of varying sizes living in our system.
- Root silhouettes and dripping water can be seen through the tarp of our vertical grow bed.
- Growing plants at eye level eliminates the need to bend down when harvesting, a common challenge of traditional gardening.
- One of the biggest issues with commercial aquaponics systems is the cost of supplemental lighting. Our system uses two LED grow lights as opposed to standard fluorescent bulbs which keeps lighting costs to a minimum.
FLOOD + DRAIN BED
Our first grow bed is a traditional flood and drain bed used in many commercial aquaponics systems. Using a plastic bin filled with expanded clay pellets and a bell syphon, the bed is designed to fill with water then automatically flush back into the fish tank. This constant flooding and draining allows the plants’ roots to get adequate amounts of both water and oxygen.
VERTICAL GROW WALL
Our second bed is a vertical grow wall made of net cups and woven tarpaulin stretched over a PVC frame. Water is pumped through the PVC frame and drips over the net cups with roots and clay pellets in them. This grow wall was inexpensive to build and takes up less space than the flood and drain bed.
The first step of this project was to buy our 130-gallon fish tank with money awarded to us by the RISD materials fund. We lucked out and were able to find this tank for just fifty dollars on the Facebook Marketplace. Here I am cleaning it out with baking soda.
I was excited about the prospect of making our system closed loop, meaning that it would be able to sustain itself like a pond in nature. In order to make our system closed loop, we’d have to grow our own fish food. We experimented with this by cultivating duckweed, an invasive aquatic plant that fish eat in the wild. Ultimately we prioritized other elements of the system and replaced the duckweed bed with the vertical grow wall.
All the plants in our system were grown from seed then transferred into the grow beds. Here we experimented with growing basil in three growing mediums: gravel, vermiculite, and potting soil. Ultimately the plants grown in potting soil performed the best and were transplanted into our grow beds.
In my opinion, the hardest part of aquaponics is balancing water between the various tanks and grow beds. Making sure that water flows through the system without overflowing or draining your fish tank is a basic requirement, but essential to the success of your system. These three plastic bins were our first attempt at this balancing act.