Just as with the aquarium microcosms, our goal is to make each of our Winogradsky column microcosms as similar as possible, other than differences in added nutrients. With the exception of one control Winogradsky column, which contains only unenriched sediment, each of the other Winogradsky columns begins with sufficient enriched sediment to fill the column roughly half full. To that, we’ll add add about half as much unenriched sediment to fill the column to a total of about three quarters. Finally, we’ll fill the column with pond or stream water, leaving a small air gap.