Towering above the crowd, Rik Kretzinger’s PVC aquaponics tower supports a garden of little plants — strawberries, chives, and cilantro, in this case — on the waste of a few fish, broken down by bacteria. AGponics, as its called, is a modular system, so many of these towers can be lined up and controlled by Arduino with the help of sensors in the tower. Really, it’s a robotic farm, says Kretzinger, complete with internet connectivity so it can email him if something goes wrong.