Abstract: An apparatus for supporting a window in a fluid container formed by a plurality of wall blocks attached by curable material is disclosed. The apparatus has a frame member including a container flange configured to abut against at least some of the plurality of wall blocks, a plurality of posts disposed at the container flange and configured to be received in the curable material disposed between the plurality of wall blocks, a retainer member, and a plurality of fasteners. The retainer member is configured to be attached to the frame member based on the plurality of fasteners being received through a plurality of apertures of the container flange and a plurality of apertures of the retainer member and by being received in the plurality of posts.