Abstract: There is provided an apparatus for clarifying fluid in a fluid container, e.g., a tank, basin or lagoon. The apparatus comprises a first means for defining a quiescent zone in the container. The first means includes a pair of end walls, a pair of side walls, and a bottom wall comprising at least one surface having open and closed areas to permit settled solids to pass out of the quiescent zone. Means are provided to introduce fluid containing suspended solids into the quiescent zone. Preferably, the bottom wall also permits fluid containing suspended solids to pass into the quiescent zone. For instance, the bottom wall may comprise spaced, sloping surfaces extending across the bottom. A second means is located below the first means and defines a fluid flow path below and in communication with the bottom wall of the quiescent zone. The second means has both an inlet and an outlet.