Sump

[gregzz4]

I hope you're planning on replacing the baffles with glass.
I'd suggest 1/4".
I'd also suggest waiting at least 72 hours after installing them before you put water back in, and use a fan to blow room air through your stand to 'air out' the silicone fumes. This will help speed up the curing time. The silicone needs to interact with the surrounding air to cure.

If you're going to go with 1/4" plexi again, look for some rubber strips that wrap the edges of the plex. These are similar to what window glass installers use and you can use them to 'pressure fit' the plex into place.
This product is a 'channel' that wraps the edge of the plex with flat outer edges.
Just do some research on it being 'potable', but I've seen threads where it's been used long-term successfully.