An additional anaerobic layer, this time of unsupplemented mud, brings the container to two thirds full. Alternatively, some procedures call for sand to be used for the layer above the enriched sediment as to allow for easier observation and sampling of resulting populations.
An extra anaerobic layer, consisting of unsupplemented mud, raises the container to two-thirds full. Alternatively, some methods require sand to be placed above the enriched sediment for better observation and sampling of resulting populations.