I think you'd be fine and I would encourage you to try it out. I would suggest using Weldon 4 instead of the 16. You could use the 16 as extra insurance on the inside seams but it isn't necessary.
The trick to putting an acrylic aquarium together is to use good acrylic and to have good, finished edges. For such a small aquarium, almost any acrylic would do but for something bigger I would suggest domestic, clear-cast acrylic. I also prefer to go with 1/4 inch just to be sure I won't get a bulging aquarium.
To get a good edge, have a professional cut it to your dimensions AND tell them to route the edges clean. If you're doing it yourself, you need an acrylic blade in your saw and a good straight edge router bit to eliminate the rough edges.
Build the sides first and then the bottom. Glue using the acrylic needle dispensers while slightly lifting the side using pins. Pull the pins after you've applied the glue and hold the piece straight with something. A little weight on top to push out the bubbles also helps.
Hope that helps.