Well I decided to go with MDF which is smooth and hard. It can get messed up if wet but I'll take my chances. I used 1/2 inch 2 x4 foot boards cut down to fint just inside the rim and notched around the post. Only have one installed so far. I put my row of 10 verts on it. Looks much better and I feek better about the tanks sitting on it.
I thought about painting the boards black but the wife said no. I think she wants the project done as now I have two rooms all messed up.
Thanks for you ideas! I might employ them in the future.