Hi Alan, I made most of my old tanks, using glass and silicon sealant, the down side of glass is the weight, but I found the times I used acrylic didn't work, as the acrylic wasn't very strong and the seal used to come apart over time.and the front had an annoying habit of warping over time.
I don't know what metaframe is, but if you do use acrylic, I would glue the sides with acrylic solvent, this should strengthen the cube, Also be careful with the base, it will need a solid surface to stop any movement or sagging on the acrylic base.
hope this input helps.