When I first started visiting the Urban Organics indoor aquaponics farm in St. Paul last September for the article “The Indoor Aquaponics Farm,” the massive Stock House #3 was an empty shell waiting to be filled with tanks, racks, filters and monitoring systems...and eventually fish and plants.
Ten months later and the first floor of this five-story vertical farm is now fully built out. Last Friday, co-founder Dave Haider showed me the main fish tanks (above) that had been filled with water, which was cycling through the filtering system and still-empty plant racks (also above). After showing me the monitoring systems that will alert Haider and his colleagues when, say, the ph levels or water temperature have gone out of bounds, we walked a few shorts steps to the finishing tanks where the mature tilapia will spend their final days before going to market.
Right now the tanks are home to a couple dozen black and white tilapia, which Haider had grown from fingerlings in a couple of small tanks on the second floor. He told me these fish were also contributing to the cycling of the system and indeed, when Haider fed the fish, they almost immediately began pooping, just a small demonstration of what will be happening in the large tanks after they are stocked with 1000-2000 fish each in a few weeks.
Haider explained that idea of “cycling the system” is to nurture and vastly expand the population of the naturally occurring Nitrosomonas bacteria with the sustenance they need—ammonia—which they convert to nitrites.
Those nitrites are lunch for their cousins, Nitrobacter, which convert the nitrites to nitrates, food for the plants that Haider’s team plans to grow here starting by the middle of August. The moving bed biofilter (below), where Nitrosomonas and Nitrobacter will be living and working on tiny plastic paddlewheels, was slowly filling with water flowing from the main fish tanks, the blowers aerating the mass of plastic that burbled and glurged like a cauldron of bubbling white lava.
For a better understanding of how the whole system will work when Urban Organics opens for business in October, check out the interactive infographic: