Acrylic glue. I made 6 pieces of acrylic and notched a cut out for the pipe and glue it in place. I didn't want to use any eggcrate and wanted something I could remove easily so that is what I came up with
I had a chance to visit Duke today and see his reef ----- boy those 3 pictures above don't do justice - awesome colors , great aqua scape , nice fish selection --- really liked it