I imagine it is much easier to laminate acrylic with acrylic without leaving a visible lamination than it is to do so with acrylic and glass. They probably simply fuse the layers with something similar to weld-on. As far as fusing glass to acrylic, I don't know what you'd use. Even if you could find something that works well, there is the issue of how the two materials react differently to strain. Glass and acrylic have very different mechanical properties. On most acrylic tanks, the sides bend fairly noticeably. This is fine for acrylic (assuming that it is properly constructed and of a sufficient thickness) as acrylic has a fairly high yield strain. Glass, on the other hand, is fairly brittle and can break with relatively little strain. I suppose you could combine rather thick acrylic with thin glass, it would take some experimenting to get it right.