The Sludge Gun from Markland Specialty Engineering helps operators measure solid-liquid interface levels in lagoons, clarifiers and tanks. It can be used to monitor sludge bed depth for regulatory compliance and prevention of carryover, and to pump/dredge only when necessary. It uses an LED and phototransistor sensor pairing to detect biosolids in densities ranging from light flocs to thick blankets. A thumb-adjustable control allows the user to fine-tune the probe’s sensitivity. It emits an audible tone that varies in volume and pitch, depending on the concentration of suspended solids. Users establish the location of both the true settled bed and the overlying unsettled cloudy layer by observing the numbered depth markers on the cable as the probe is lowered into the pond or tank. It is ideal for use from boats and catwalks. No calibration is required. 855/873-7791; www.sludgecontrols.com