— We present an integral feedback controller that regulates the average copy number of a particular assembly in a system of stochastically interacting robots. The mathematical model for the stochastic system is a tunable reaction network, which makes this approach applicable to a large class of other systems, including ones that exhibit stochastic self assembly at various length scales. We prove that this controller works for a range of set-points, and how to compute this range. Finally, we demonstrate the approach on a physical testbed.