Microthrix is a thread-forming bacterium and can cause the formation of light sludge in wastewater treatment plants. Frequent measurement of Microthrix makes it possible to react quickly and in a timely manner to the formation of light sludge. The target tube measures a wide range of filamentous species, including Microthrix parvicella. Target Tubes are packed per 50 pieces and are ready to use. The shelf life is at least 1 year at room temperature, if stored in the dark.