Amoeba vary in size and move due to their “false feet”. Amoeba grow well on particulate organic material, are very hardy, and can survive in low DO environments. A bloom in amoebae can indicate an increase in particulate organic matter. Some species contain shells, which are called testate amoeba. Testate amoeba tend to occur over most F/M ranges, while the non-testate amoeba are often found in younger sludge and high F/M ratios.