Nice job! I made a
clear reservoir and stuck laser lights under it. Not for everyone but I like it.
Lexan is easier to drill and tap than plexi, but it can be done and not leak.
When I first made a reservoir out of lexan I used a water proof epoxy and it started to leak at one corner after a couple of months. It wasn't a marine epoxy though so I hope you don't have that happen to you.
I made the second reservoir out of plexi and used
ISP Weld On # 16 cement. Won't fill gaps but creates a chemical bond.