Epoxy is reef safe, however I still wouldn't use it for acrylic to glass. Acrylic swells and shrinks and epoxy is too rigid. What you want to use is a special silicone caulk made for plastics. You can find it at HD in the acrylic sheet department....not in the paint department with all the other silicones. This stuff is a must for acrylic baffles! Looks like this:
About 8 bucks a tube. Just give it time to cure....minimum three days, but I prefer a week (or more).
And I see this is your first post.....WELCOME to R2R. You're going to like it here.