The tank is glass, so it only needs support around the edge. I was originally going to cover the top with a piece of plywood, but if I leave the exposed metal that would make the edge visible, which isn't ideal. I like the idea of a yoga / camping mat, but I'm curious if the plywood is necessary if the metal is on plane. Does the wood serve more than that?
One advantage to using plywood is it gives you the option of mounting a light underneath so you can see what is inside the stand especially if using a sump.
If it were me I would not worry about the plywood for a glass tank on that stand. I would probably look at strips of solid rubber of very dense closed cell foam. There is no use putting a mat under the entire tank if only the edges are being supported.
Just to close this out, got the stand FINISHED this weekend. Here are some of the final pics. I'm excited with how it turned out.
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The stand looks amazing! Care to share how much the materials cost? I’m planning a 180 stand too and still deciding between square tubing or wood frame.