m-TGE (Tryptone Glucose Extract) with TTC is a non-selective medium used for the determination of heterotrophic plate counts by the membrane filtration method and specified by the American Public Health Association for the heterotrophic plate count procedure in testing bottled water. It is also used for isolation, detection and cultivation of wide variety of microorganisms in beverages, ground, surface and recreational waters, milk and other dairy products. TTC (2,3,5-triphenyltetrazolium chloride) is added to the medium to make colonies easier to identify. All colonies that grow on the surface of the membrane are counted and recorded. Most colonies will appear pink to red due to the reduction of TTC, though some may be yellow to orange (a range of different colony appearances may be seen in a single sample). Incubation is typically at 30–35 °C for 18-72 hours (with longer incubation times recommended for bottled water).