freckleface acrylics for sump?

There is so much involved with making even a simply box from acrylic that you really need experience w/ at least woodworking as stated above. It's more than gluing pieces together. There are some good instructional vids on tap plastics web site.
You'll want to use cell cast acrylic imo. I honestly believe you could contact a company like glasscages and have a custom built sump made for not much more than buying materials and building it yourself. Have to warn you though that the owner of glasscages isn't the most pleasant person to work with.