Written by guest blogger, Dan Divelbiss, one of the masterminds behind the Zoo’s aquaponics system.
“Waste” does not exist in nature. All our furred, feathered, and finned friends don’t take a trash can out to the curb each week to watch their undesirables go “away”. Instead nature has a plan for every scrap and left-over. As we learn from nature, we too can begin to apply this concept to our lives. If you were recently walking past the Base Camp Café on your way to Africa, you may have noticed a greenhouse filled with water, fish, and plants. This is the Zoo’s newest effort synergize with nature’s design ethic: Aquaponics!
Simply stated, aquaponics is growing fish to eat (aquaculture) and vegetables (hydroponics) together, where wastes from the fish are food for the plants, and the plants clean the water for the fish. In this controlled environment, yields are high and reliable. Aquaponics systems range from simple, tabletop systems consisting of little more than goldfish and a few sprigs of basil to elaborate, commercial scale systems which employ many people and produce tons of food annually. This particular aquaponics system in the Greenhouse was designed to show how folks can build their own family-scale, aquaponic garden from materials available at local hardware/landscaping stores.
This system consists of a fish tank, two grow beds for vegetables, a pump, an aerator, solids filter, and a biofilter. Water flows through the system continuously in a closed-loop allowing nutrients and water to be cycled and recycled. If this system were meant to accommodate a higher fish density (aka more “waste” producers in the same space), it would require a few more components. However, this system with a low fish population and extensive biofiltration doesn’t require them.
Fish are housed in a tank. Water from the fish tank is pumped through solids removal and into a biofilter, where the fish waste is converted by bacteria from ammonia (possibly toxic to fish) into nitrates (non-toxic to fish) that can be used by plants. The water flows downhill from the biofilter into growing trays. Plants grow in beds of gravel or expanded clay (which also acts as an additional biofilter), or they are floated on the water in a floating raft. After the water passes through a network of plant roots, it is returned, cleansed, to the fish tank. All through the process, air is pumped into the system to ensure plenty of oxygen for the fish, beneficial bacteria, and plants. Each day the fish are fed and their excrement supplies the nutrients necessary for plant growth.
The current plants growing in the aquaponics system include basil, cucumber, and tomato. Each day, our SSA chefs harvest what they need for catering and restaurant meals, staying true to their commitment to providing our guests food that is as fresh and as local possible. For example, your caprese salad features basil grown in the Greenhouse, and picked just before it is tossed in your salad.
If you’d like to learn more about aquaponics, stop by the Zoo and check out this new exhibit next to the Base Camp Café. The Greenhouse was made possible by the Woodward Family Charitable Foundation.
Dan Divelbiss, MS is the managing member of Waterfields, LLC, an urban agriculture development company focusing on bringing commercial aquaponics to the urban core to create living wage jobs, revitalize communities, and sell to Cincinnati’s local food market. Learn more at www.waterfieldsllc.com