A weir assembly system comprises an insert dimensioned to be inserted into a section of a wellbore and a plurality of weirs spaced within the insert so as to increase the separation of solids from fluid within the section of the wellbore when the fluid is flowing through the wellbore. The plurality of weirs may be oriented to create a tortuous fluid flow path, such that a flow opening of a first weir causes solids to deposit at a second weir without obstructing a flow opening of the second weir. Additional apparatus, methods, and systems are disclosed.