Inside A Casper School Turned Farm That’s Growing Affordable Food With Fish Poop

A Casper farm is turning fish poop into food inside a former elementary school that also operates as a hybrid classroom and gathering space. Urban Thistle, an urban farm and food hub run through the Casper Housing Authority, doesn’t waste anything—not even the waste of its fish.

Inside the aquaponics room, the steady hum of water pumps fills the air. Bright green ginger sprouts and stalks of hot pink chard glow under LED grow lights, anchored in gravel beds above large fish tanks. Each morning begins with feeding the tilapia, which quickly rise to the surface expecting breakfast. Staff carefully monitor water temperature, pH, and nutrient levels like ammonia and nitrates, troubleshooting everything from clogged filters to failing pumps.

Fish poop is the key to the whole operation. Fish naturally produce nutrient-rich waste that becomes fertilizer, while plants simultaneously filter and clean the water before it cycles back into the tanks. The result is a soil-free, closed-loop system that can support multiple edible plants in a small footprint. Behind the scenes, tiny, naturally occurring bacteria break down ammonia from fish waste into nitrates—a form of nutrients plants can easily absorb. The process, known as the nitrogen cycle, happens naturally in lakes and rivers; at Urban Thistle, it is simply being harnessed indoors.

Program director Jamie Purcell said the tilapia are hardy fish well suited for the setup, and some of the larger ones are nearly ready for harvest. Alongside tilapia, staff are raising chard, spider plants, cabbage, Brussels sprouts, ginger, and kale. One pleasant surprise has been the chard, which has grown to what they jokingly call “Jurassic” size. The Brussels sprouts have produced strong vines but little in the way of actual sprouts so far.

Although the aquaponics system is relatively new, the farm’s hydroponic towers are already filling boxes with food. Staff recently harvested about 80 pounds of greens, distributed through the Casper Housing Authority CARES Pantry Program for local tenants, with additional produce donated to the nearby Holy Cross Food Bank.

The idea grew out of a practical challenge: growing food through Wyoming winters can be expensive, especially when traditional soil gardens require large amounts of heat. By shifting to water-based systems and stacking plants vertically, the farm can focus energy where it matters most while using existing indoor space that is already climate controlled.

Purcell said learning to manage the system was a challenge. “You have to have the right flow of water to each grow bed,” she said. “That flow can be affected by the pump’s performance, or the filter, or so many variables. Learning how to get everything balanced has been a big learning curve—but today we feel we have mastered the challenge.”

At its core, Purcell said Urban Thistle sees gardening as more than just growing food; it is about growing community. “We hope that we are doing that work every day and that it continues to build each year, making this farm the community’s,” she said.