Methods and related systems are described relating to monitoring particulates downhole at in-situ conditions. Solid particles being carried in the fluid as the fluid is produced from the reservoir formation are monitored. The downhole solid particle monitoring can include measuring the quantity (e.g., volume fraction, weight fraction, or the like) of solid particles, measuring the distribution of sizes of the solid particles, and/or measuring the shape of the particles. The solid particles can be monitored using one or more of sensors such as optical spectrometers, acoustic sensors, video cameras, and erosion probes. A sanding prediction is generated based at least in part on the monitoring of the solid particles, and the sanding prediction is then used to design a completion, lift system, and surface facilities for the wellbore and/or select operating conditions so as to control sanding during production.