This is a cool acrylic top I saw on someone's set-up so I got some mesh from a guy in the states (if your watching this feel free to post a link to your thread).
I ordered my acrylic... and like my glass nobody wants to give me what I want (they say it's too hard/too much work/they can't do it cause it shatters at that width)... so I buy a saw and an 80 dollar blade and cut it myself (at 1/2" in width there was not even a chip). Then I put it all together.
The saw and the pieces I cut.
The first step is to make the bottom rectangle. If you notice the piece that I put on top of the box is the full width. Making the boxes staggered like that helps to avoid weak spots.
Then you stretch the mesh on the one side and glue/clamp the top piece on.
Then you pull the mesh tight to the other side and stretch it width wise at the same time (difficult to do solo without the right tools).
The you do either side pulling it tight (you may get some mild warping) then put the tabs on to make sure it doesn't fall into your tank.