Here is a photo of a small (4" X 6" X 8" high) acrylic Hang On Tank refugium with Mangrove seedlings, being used to reduce nitrates, phosphates and other toxins in a 55g saltwater tank. The plumbing is simple: a siphon tube and a small plastic hose from the top of a powerhead. This refugium can be hung anywhere on the outside of a tank or sump. You can also drill some holes in it and hang it on the inside of a tank or sump, which requires no plumbing.
Refugiums can be constructed of glass, acrylic or just about anything else that will hold water, however here we are going to show you how to build a Hang In/On Tank Refugium using 3/16" Cell Cast Acrylic.