Dividing a tank.

[bounce]

I would use 1/8th in plexi maybe 1/4 but thicker than that will be difficult,
to make it modular you could cut notches into the pieces so that they interlock, and not seal them with the silicone then you can remove and change them if you need. If you are cutting it yourself you can use the score and crack method which will not be volatile, but anything with power tools you should probably wear a vapor respirator because the fumes are nasty. My favorite thing to cut plex with is an oscillating power tool then a file to clean the edges.

[BerserkApe]

I would use 1/8th in plexi maybe 1/4 but thicker than that will be difficult,
to make it modular you could cut notches into the pieces so that they interlock, and not seal them with the silicone then you can remove and change them if you need. If you are cutting it yourself you can use the score and crack method which will not be volatile, but anything with power tools you should probably wear a vapor respirator because the fumes are nasty. My favorite thing to cut plex with is an oscillating power tool then a file to clean the edges.

Tablesaw with fine teeth, sanding edges, then covering with electrical tape.