Those frames are great! How did you do that?
I just cut out the outside perimeter square out of a piece of 3/8" cast acrylic using the table saw. Then I moved the fence over a bit and cut out the inside square, and to get the track for the spline that holds in the mesh, I just lowered my saw blade to cut about half the thickness of the acrylic and made another pass.
guess I should mention that these are just going to sit on top of the tank, not fit directly into the openings, and I only say that because acrylic will warp if it stays in constant contact with the water, so I'm hoping that by having the acrylic a couple inches from the opening that it will keep it from warping. However if it doesn't I can always bond some tabs to the top of the tank to hold it in place I LOVE working with acrylic LOL Its so much more versatile than glass!
If you are not looking to diy and you want some tops like these you should check out @ArtFully Acrylic they have some amazing polycarbonate screen tops, and they can custom make them to fit your exact tank. I'm hoping that these work for me, but if not I'll be saving up my pennies to get a set from them. If I only had a CNC ;D