Building a sump/refugium is so much easier then most people think.
1. Get a glass aquarium the size you want for the sump
2. Design the sump/refug the way you want it
3. Goto your local glass shop & have them cut 1/4 pieces of glass the sizes you want for your bulkheads, baffles, bubble traps etc.
4. Completely clean the aquarium using denatured alcohol
5. Place your pieces of glass in the aquarium & hold them in place using pieces of stryofoam
6. Generously apply silicon (100% rubber silicon used for doors & windows, not the sink & tub type) to the seams of the glass & aquarium.
7. W/ light pressure using your index finger, push the silicon into the joints the same way you do when applying caulking
8. (& most important IMO) LET THE SILICON DRY FOR AT LEAST 48 HOURS BEFORE REMOVING THE STYROFOAM OR MOVING THE TANK.
That's it.............You have your own custom sump/fuge & you havent donated hundreds of dollars to your LFS....